diff --git a/browser/components/extensions/ext-windows.js b/browser/components/extensions/ext-windows.js
index fbc7045e3a58..806a99796940 100644
--- a/browser/components/extensions/ext-windows.js
+++ b/browser/components/extensions/ext-windows.js
@@ -39,12 +39,16 @@ extensions.registerSchemaAPI("windows", "addon_parent", context => {
         let lastOnFocusChangedWindowId;
 
         let listener = event => {
-          let window = WindowManager.topWindow;
-          let windowId = window ? WindowManager.getId(window) : WindowManager.WINDOW_ID_NONE;
-          if (windowId !== lastOnFocusChangedWindowId) {
-            fire(windowId);
-            lastOnFocusChangedWindowId = windowId;
-          }
+          // Wait a tick to avoid firing a superfluous WINDOW_ID_NONE
+          // event when switching focus between two Firefox windows.
+          Promise.resolve().then(() => {
+            let window = Services.focus.activeWindow;
+            let windowId = window ? WindowManager.getId(window) : WindowManager.WINDOW_ID_NONE;
+            if (windowId !== lastOnFocusChangedWindowId) {
+              fire(windowId);
+              lastOnFocusChangedWindowId = windowId;
+            }
+          });
         };
         AllWindowEvents.addListener("focus", listener);
         AllWindowEvents.addListener("blur", listener);
diff --git a/browser/components/extensions/test/browser/browser_ext_windows_events.js b/browser/components/extensions/test/browser/browser_ext_windows_events.js
index aa3467e8ea09..ac152b084837 100644
--- a/browser/components/extensions/test/browser/browser_ext_windows_events.js
+++ b/browser/components/extensions/test/browser/browser_ext_windows_events.js
@@ -16,10 +16,15 @@ add_task(function* testWindowsEvents() {
       browser.test.sendMessage("window-created", window.id);
     });
 
-    let lastWindowId;
+    let lastWindowId, os;
     browser.windows.onFocusChanged.addListener(function listener(windowId) {
       browser.test.log(`onFocusChange: windowId=${windowId} lastWindowId=${lastWindowId}`);
 
+      if (windowId === browser.windows.WINDOW_ID_NONE && os === "linux") {
+        browser.test.log("Ignoring a superfluous WINDOW_ID_NONE (blur) event on Linux");
+        return;
+      }
+
       browser.test.assertTrue(lastWindowId !== windowId,
                               "onFocusChanged fired once for the given window");
       lastWindowId = windowId;
@@ -43,7 +48,10 @@ add_task(function* testWindowsEvents() {
       browser.test.notifyPass("windows.events");
     });
 
-    browser.test.sendMessage("ready");
+    browser.runtime.getPlatformInfo(info => {
+      os = info.os;
+      browser.test.sendMessage("ready");
+    });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
diff --git a/caps/nsScriptSecurityManager.cpp b/caps/nsScriptSecurityManager.cpp
index 5e27e73728f6..2a60221726dd 100644
--- a/caps/nsScriptSecurityManager.cpp
+++ b/caps/nsScriptSecurityManager.cpp
@@ -154,8 +154,8 @@ inline void SetPendingExceptionASCII(JSContext *cx, const char *aMsg)
 
 inline void SetPendingException(JSContext *cx, const char16_t *aMsg)
 {
-    // FIXME: Need to convert to UTF-8 (bug XXX).
-    JS_ReportErrorLatin1(cx, "%hs", aMsg);
+    NS_ConvertUTF16toUTF8 msg(aMsg);
+    JS_ReportErrorUTF8(cx, "%s", msg.get());
 }
 
 // Helper class to get stuff from the ClassInfo and not waste extra time with
diff --git a/devtools/client/animationinspector/test/browser.ini b/devtools/client/animationinspector/test/browser.ini
index c8d111b120db..8d6343612f24 100644
--- a/devtools/client/animationinspector/test/browser.ini
+++ b/devtools/client/animationinspector/test/browser.ini
@@ -48,8 +48,9 @@ skip-if = os == "linux" && !debug # Bug 1227792
 [browser_animation_timeline_currentTime.js]
 [browser_animation_timeline_header.js]
 [browser_animation_timeline_iterationStart.js]
-[browser_animation_timeline_pause_button.js]
-skip-if = os == "linux" && bits == 32 # Bug 1220974
+[browser_animation_timeline_pause_button_01.js]
+[browser_animation_timeline_pause_button_02.js]
+[browser_animation_timeline_pause_button_03.js]
 [browser_animation_timeline_rate_selector.js]
 [browser_animation_timeline_rewind_button.js]
 [browser_animation_timeline_scrubber_exists.js]
diff --git a/devtools/client/animationinspector/test/browser_animation_timeline_pause_button.js b/devtools/client/animationinspector/test/browser_animation_timeline_pause_button.js
deleted file mode 100644
index 4bded733ac7f..000000000000
--- a/devtools/client/animationinspector/test/browser_animation_timeline_pause_button.js
+++ /dev/null
@@ -1,110 +0,0 @@
-/* vim: set ts=2 et sw=2 tw=80: */
-/* Any copyright is dedicated to the Public Domain.
- http://creativecommons.org/publicdomain/zero/1.0/ */
-
-"use strict";
-
-requestLongerTimeout(2);
-
-// Check that the timeline toolbar contains a pause button and that this pause
-// button can be clicked. Check that when it is, the current animations
-// displayed in the timeline get their playstates changed accordingly, and check
-// that the scrubber resumes/stops moving.
-// Also checks that the button goes to the right state when the scrubber has
-// reached the end of the timeline: continues to be in playing mode for infinite
-// animations, goes to paused mode otherwise.
-// And test that clicking the button once the scrubber has reached the end of
-// the timeline does the right thing.
-
-add_task(function* () {
-  yield addTab(URL_ROOT + "doc_simple_animation.html");
-
-  let {panel, inspector} = yield openAnimationInspector();
-  let timeline = panel.animationsTimelineComponent;
-  let btn = panel.playTimelineButtonEl;
-
-  ok(btn, "The play/pause button exists");
-  ok(!btn.classList.contains("paused"),
-     "The play/pause button is in its playing state");
-
-  info("Click on the button to pause all timeline animations");
-  yield clickTimelinePlayPauseButton(panel);
-
-  ok(btn.classList.contains("paused"),
-     "The play/pause button is in its paused state");
-  yield assertScrubberMoving(panel, false);
-
-  info("Click again on the button to play all timeline animations");
-  yield clickTimelinePlayPauseButton(panel);
-
-  ok(!btn.classList.contains("paused"),
-     "The play/pause button is in its playing state again");
-  yield assertScrubberMoving(panel, true);
-
-  // Some animations on the test page are infinite, so the scrubber won't stop
-  // at the end of the timeline, and the button should remain in play mode.
-  info("Select an infinite animation, reload the page and wait for the " +
-       "animation to complete");
-  yield selectNodeAndWaitForAnimations(".multi", inspector);
-  yield reloadTab(inspector);
-  yield waitForOutOfBoundScrubber(timeline);
-
-  ok(!btn.classList.contains("paused"),
-     "The button is in its playing state still, animations are infinite.");
-  yield assertScrubberMoving(panel, true);
-
-  info("Click on the button after the scrubber has moved out of bounds");
-  yield clickTimelinePlayPauseButton(panel);
-
-  ok(btn.classList.contains("paused"),
-     "The button can be paused after the scrubber has moved out of bounds");
-  yield assertScrubberMoving(panel, false);
-
-  // For a finite animation though, once the scrubber reaches the end of the
-  // timeline, it should go back to paused mode.
-  info("Select a finite animation, reload the page and wait for the " +
-       "animation to complete");
-  yield selectNodeAndWaitForAnimations(".negative-delay", inspector);
-
-  let onScrubberStopped = waitForScrubberStopped(timeline);
-  yield reloadTab(inspector);
-  yield onScrubberStopped;
-
-  ok(btn.classList.contains("paused"),
-     "The button is in paused state once finite animations are done");
-  yield assertScrubberMoving(panel, false);
-
-  info("Click again on the button to play the animation from the start again");
-  yield clickTimelinePlayPauseButton(panel);
-
-  ok(!btn.classList.contains("paused"),
-     "Clicking the button once finite animations are done should restart them");
-  yield assertScrubberMoving(panel, true);
-});
-
-function waitForOutOfBoundScrubber({win, scrubberEl}) {
-  return new Promise(resolve => {
-    function check() {
-      let pos = scrubberEl.getBoxQuads()[0].bounds.right;
-      let width = win.document.documentElement.offsetWidth;
-      if (pos >= width) {
-        setTimeout(resolve, 50);
-      } else {
-        setTimeout(check, 50);
-      }
-    }
-    check();
-  });
-}
-
-function waitForScrubberStopped(timeline) {
-  return new Promise(resolve => {
-    timeline.on("timeline-data-changed",
-      function onTimelineData(e, {isMoving}) {
-        if (!isMoving) {
-          timeline.off("timeline-data-changed", onTimelineData);
-          resolve();
-        }
-      });
-  });
-}
diff --git a/devtools/client/animationinspector/test/browser_animation_timeline_pause_button_01.js b/devtools/client/animationinspector/test/browser_animation_timeline_pause_button_01.js
new file mode 100644
index 000000000000..a3a2b4c61003
--- /dev/null
+++ b/devtools/client/animationinspector/test/browser_animation_timeline_pause_button_01.js
@@ -0,0 +1,34 @@
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+ http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+requestLongerTimeout(2);
+
+// Check that the timeline toolbar contains a pause button and that this pause button can
+// be clicked. Check that when it is, the button changes state and the scrubber stops and
+// resumes.
+
+add_task(function* () {
+  yield addTab(URL_ROOT + "doc_simple_animation.html");
+
+  let {panel} = yield openAnimationInspector();
+  let btn = panel.playTimelineButtonEl;
+
+  ok(btn, "The play/pause button exists");
+  ok(!btn.classList.contains("paused"), "The play/pause button is in its playing state");
+
+  info("Click on the button to pause all timeline animations");
+  yield clickTimelinePlayPauseButton(panel);
+
+  ok(btn.classList.contains("paused"), "The play/pause button is in its paused state");
+  yield assertScrubberMoving(panel, false);
+
+  info("Click again on the button to play all timeline animations");
+  yield clickTimelinePlayPauseButton(panel);
+
+  ok(!btn.classList.contains("paused"),
+     "The play/pause button is in its playing state again");
+  yield assertScrubberMoving(panel, true);
+});
diff --git a/devtools/client/animationinspector/test/browser_animation_timeline_pause_button_02.js b/devtools/client/animationinspector/test/browser_animation_timeline_pause_button_02.js
new file mode 100644
index 000000000000..1c440dd8815b
--- /dev/null
+++ b/devtools/client/animationinspector/test/browser_animation_timeline_pause_button_02.js
@@ -0,0 +1,48 @@
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+ http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+requestLongerTimeout(2);
+
+// Checks that the play/pause button goes to the right state when the scrubber has reached
+// the end of the timeline but there are infinite animations playing.
+
+add_task(function* () {
+  yield addTab(URL_ROOT + "doc_simple_animation.html");
+
+  let {panel, inspector} = yield openAnimationInspector();
+  let timeline = panel.animationsTimelineComponent;
+  let btn = panel.playTimelineButtonEl;
+
+  info("Select an infinite animation and wait for the scrubber to reach the end");
+  yield selectNodeAndWaitForAnimations(".multi", inspector);
+  yield waitForOutOfBoundScrubber(timeline);
+
+  ok(!btn.classList.contains("paused"),
+     "The button is in its playing state still, animations are infinite.");
+  yield assertScrubberMoving(panel, true);
+
+  info("Click on the button after the scrubber has moved out of bounds");
+  yield clickTimelinePlayPauseButton(panel);
+
+  ok(btn.classList.contains("paused"),
+     "The button can be paused after the scrubber has moved out of bounds");
+  yield assertScrubberMoving(panel, false);
+});
+
+function waitForOutOfBoundScrubber({win, scrubberEl}) {
+  return new Promise(resolve => {
+    function check() {
+      let pos = scrubberEl.getBoxQuads()[0].bounds.right;
+      let width = win.document.documentElement.offsetWidth;
+      if (pos >= width) {
+        setTimeout(resolve, 50);
+      } else {
+        setTimeout(check, 50);
+      }
+    }
+    check();
+  });
+}
diff --git a/devtools/client/animationinspector/test/browser_animation_timeline_pause_button_03.js b/devtools/client/animationinspector/test/browser_animation_timeline_pause_button_03.js
new file mode 100644
index 000000000000..ad75ab9f79b5
--- /dev/null
+++ b/devtools/client/animationinspector/test/browser_animation_timeline_pause_button_03.js
@@ -0,0 +1,54 @@
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+ http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+requestLongerTimeout(2);
+
+// Also checks that the button goes to the right state when the scrubber has
+// reached the end of the timeline: continues to be in playing mode for infinite
+// animations, goes to paused mode otherwise.
+// And test that clicking the button once the scrubber has reached the end of
+// the timeline does the right thing.
+
+add_task(function* () {
+  yield addTab(URL_ROOT + "doc_simple_animation.html");
+
+  let {panel, inspector} = yield openAnimationInspector();
+  let timeline = panel.animationsTimelineComponent;
+  let btn = panel.playTimelineButtonEl;
+
+  // For a finite animation, once the scrubber reaches the end of the timeline, the pause
+  // button should go back to paused mode.
+  info("Select a finite animation and wait for the animation to complete");
+  yield selectNodeAndWaitForAnimations(".negative-delay", inspector);
+
+  let onScrubberStopped = waitForScrubberStopped(timeline);
+  // The page is reloaded to avoid missing the animation.
+  yield reloadTab(inspector);
+  yield onScrubberStopped;
+
+  ok(btn.classList.contains("paused"),
+     "The button is in paused state once finite animations are done");
+  yield assertScrubberMoving(panel, false);
+
+  info("Click again on the button to play the animation from the start again");
+  yield clickTimelinePlayPauseButton(panel);
+
+  ok(!btn.classList.contains("paused"),
+     "Clicking the button once finite animations are done should restart them");
+  yield assertScrubberMoving(panel, true);
+});
+
+function waitForScrubberStopped(timeline) {
+  return new Promise(resolve => {
+    timeline.on("timeline-data-changed",
+      function onTimelineData(e, {isMoving}) {
+        if (!isMoving) {
+          timeline.off("timeline-data-changed", onTimelineData);
+          resolve();
+        }
+      });
+  });
+}
diff --git a/devtools/client/themes/inspector.css b/devtools/client/themes/inspector.css
index b009e4e16810..9590d5367fa8 100644
--- a/devtools/client/themes/inspector.css
+++ b/devtools/client/themes/inspector.css
@@ -105,24 +105,6 @@ window {
   flex: unset;
 }
 
-/* TODO: bug 1265759: should apply to .devtools-searchinput once all searchbox
-   is converted to html*/
-#inspector-searchbox {
-  width: 100%;
-}
-
-/* Make sure the text is vertically centered in Inspector's
-   search box. This can be removed when the search box is
-   switched to HTML.
-   See also: https://bugzilla.mozilla.org/show_bug.cgi?id=1265759 */
-.theme-dark #inspector-searchbox,
-.theme-light #inspector-searchbox {
-  line-height: 19px;
-}
-.theme-firebug #inspector-searchbox {
-  line-height: 17px;
-}
-
 /* Eyedropper toolbar button */
 
 #inspector-eyedropper-toggle {
diff --git a/dom/plugins/base/nsJSNPRuntime.cpp b/dom/plugins/base/nsJSNPRuntime.cpp
index 020cffd4e69c..d9377a70604d 100644
--- a/dom/plugins/base/nsJSNPRuntime.cpp
+++ b/dom/plugins/base/nsJSNPRuntime.cpp
@@ -638,7 +638,7 @@ ThrowJSExceptionASCII(JSContext *cx, const char *message)
 
     PopException();
   } else {
-    ::JS_ReportErrorASCII(cx, message);
+    ::JS_ReportErrorASCII(cx, "%s", message);
   }
 }
 
diff --git a/js/src/asmjs/AsmJS.cpp b/js/src/asmjs/AsmJS.cpp
index 545a95a37842..e375b49bcb7a 100644
--- a/js/src/asmjs/AsmJS.cpp
+++ b/js/src/asmjs/AsmJS.cpp
@@ -2250,7 +2250,7 @@ class MOZ_STACK_CLASS ModuleValidator
         return false;
     }
 
-    bool failfOffset(uint32_t offset, const char* fmt, ...) {
+    bool failfOffset(uint32_t offset, const char* fmt, ...) MOZ_FORMAT_PRINTF(3, 4) {
         va_list ap;
         va_start(ap, fmt);
         failfVAOffset(offset, fmt, ap);
@@ -2258,7 +2258,7 @@ class MOZ_STACK_CLASS ModuleValidator
         return false;
     }
 
-    bool failf(ParseNode* pn, const char* fmt, ...) {
+    bool failf(ParseNode* pn, const char* fmt, ...) MOZ_FORMAT_PRINTF(3, 4) {
         va_list ap;
         va_start(ap, fmt);
         failfVAOffset(pn->pn_pos.begin, fmt, ap);
@@ -2944,7 +2944,7 @@ class MOZ_STACK_CLASS FunctionValidator
         return m_.fail(pn, str);
     }
 
-    bool failf(ParseNode* pn, const char* fmt, ...) {
+    bool failf(ParseNode* pn, const char* fmt, ...) MOZ_FORMAT_PRINTF(3, 4) {
         va_list ap;
         va_start(ap, fmt);
         m_.failfVAOffset(pn->pn_pos.begin, fmt, ap);
@@ -4720,7 +4720,8 @@ static bool
 CheckSignatureAgainstExisting(ModuleValidator& m, ParseNode* usepn, const Sig& sig, const Sig& existing)
 {
     if (sig.args().length() != existing.args().length()) {
-        return m.failf(usepn, "incompatible number of arguments (%u here vs. %u before)",
+        return m.failf(usepn, "incompatible number of arguments (%" PRIuSIZE
+                       " here vs. %" PRIuSIZE " before)",
                        sig.args().length(), existing.args().length());
     }
 
diff --git a/js/src/asmjs/WasmBinary.cpp b/js/src/asmjs/WasmBinary.cpp
index 4c1946583a6c..c14ad19dbc87 100644
--- a/js/src/asmjs/WasmBinary.cpp
+++ b/js/src/asmjs/WasmBinary.cpp
@@ -41,7 +41,8 @@ Decoder::fail(const char* msg, ...) {
 bool
 Decoder::fail(UniqueChars msg) {
     MOZ_ASSERT(error_);
-    UniqueChars strWithOffset(JS_smprintf("at offset %zu: %s", currentOffset(), msg.get()));
+    UniqueChars strWithOffset(JS_smprintf("at offset %" PRIuSIZE ": %s",
+                                          currentOffset(), msg.get()));
     if (!strWithOffset)
         return false;
 
@@ -57,7 +58,7 @@ wasm::DecodePreamble(Decoder& d)
         return d.fail("failed to match magic number");
 
     if (!d.readFixedU32(&u32) || u32 != EncodingVersion)
-        return d.fail("binary version 0x%lx does not match expected version 0x%lx",
+        return d.fail("binary version 0x%" PRIx32 " does not match expected version 0x%" PRIx32,
                       u32, EncodingVersion);
 
     return true;
@@ -151,7 +152,7 @@ wasm::DecodeLimits(Decoder& d, Limits* limits)
     // TODO (bug 1310149): tighten this check (s/3/1) when the AngryBots demo
     // gets updated.
     if (flags & ~uint32_t(0x3))
-        return d.fail("unexpected bits set in flags: %lu", (flags & ~uint32_t(0x3)));
+        return d.fail("unexpected bits set in flags: %" PRIu32, (flags & ~uint32_t(0x3)));
 
     if (!d.readVarU32(&limits->initial))
         return d.fail("expected initial length");
@@ -163,7 +164,7 @@ wasm::DecodeLimits(Decoder& d, Limits* limits)
 
         if (limits->initial > maximum) {
             return d.fail("memory size minimum must not be greater than maximum; "
-                          "maximum length %lu is less than initial length %lu",
+                          "maximum length %" PRIu32 " is less than initial length %" PRIu32 ,
                           maximum, limits->initial);
         }
 
diff --git a/js/src/asmjs/WasmBinary.h b/js/src/asmjs/WasmBinary.h
index b81121a8b42e..40ad205f73f3 100644
--- a/js/src/asmjs/WasmBinary.h
+++ b/js/src/asmjs/WasmBinary.h
@@ -778,7 +778,7 @@ class Decoder
         error_(error)
     {}
 
-    bool fail(const char* msg, ...);
+    bool fail(const char* msg, ...) MOZ_FORMAT_PRINTF(2, 3);
     bool fail(UniqueChars msg);
     void clearError() {
         if (error_)
diff --git a/js/src/asmjs/WasmBinaryIterator.h b/js/src/asmjs/WasmBinaryIterator.h
index 9a9bf1edfa06..ae244044225c 100644
--- a/js/src/asmjs/WasmBinaryIterator.h
+++ b/js/src/asmjs/WasmBinaryIterator.h
@@ -725,7 +725,7 @@ template <typename Policy>
 bool
 ExprIter<Policy>::fail(const char* msg)
 {
-    return d_.fail(msg);
+    return d_.fail("%s", msg);
 }
 
 template <typename Policy>
diff --git a/js/src/asmjs/WasmCode.cpp b/js/src/asmjs/WasmCode.cpp
index 3b0b37c8c1af..619dba2b921e 100644
--- a/js/src/asmjs/WasmCode.cpp
+++ b/js/src/asmjs/WasmCode.cpp
@@ -796,8 +796,10 @@ Code::ensureProfilingState(JSContext* cx, bool newProfilingEnabled)
             if (!name.append('\0'))
                 return false;
 
-            UniqueChars label(JS_smprintf("%hs (%s:%u)",
-                                          name.begin(),
+            TwoByteChars chars(name.begin(), name.length());
+            UniqueChars utf8Name(JS::CharsToNewUTF8CharsZ(nullptr, chars).c_str());
+            UniqueChars label(JS_smprintf("%s (%s:%u)",
+                                          utf8Name.get(),
                                           metadata_->filename.get(),
                                           codeRange.funcLineOrBytecode()));
             if (!label) {
diff --git a/js/src/asmjs/WasmTextToBinary.cpp b/js/src/asmjs/WasmTextToBinary.cpp
index 822654924e8f..6ac574544680 100644
--- a/js/src/asmjs/WasmTextToBinary.cpp
+++ b/js/src/asmjs/WasmTextToBinary.cpp
@@ -1488,7 +1488,7 @@ struct WasmParseContext
     {}
 
     bool fail(const char* message) {
-        error->reset(JS_smprintf(message));
+        error->reset(js_strdup(message));
         return false;
     }
     ~WasmParseContext() {
@@ -3336,12 +3336,9 @@ class Resolver
         return false;
     }
     bool failResolveLabel(const char* kind, AstName name) {
-        Vector<char16_t, 0, SystemAllocPolicy> nameWithNull;
-        if (!nameWithNull.append(name.begin(), name.length()))
-            return false;
-        if (!nameWithNull.append(0))
-            return false;
-        error_->reset(JS_smprintf("%s label '%hs' not found", kind, nameWithNull.begin()));
+        TwoByteChars chars(name.begin(), name.length());
+        UniqueChars utf8Chars(CharsToNewUTF8CharsZ(nullptr, chars).c_str());
+        error_->reset(JS_smprintf("%s label '%s' not found", kind, utf8Chars.get()));
         return false;
     }
 
diff --git a/js/src/builtin/Profilers.cpp b/js/src/builtin/Profilers.cpp
index 227891d88092..0d30a1c6b09f 100644
--- a/js/src/builtin/Profilers.cpp
+++ b/js/src/builtin/Profilers.cpp
@@ -41,9 +41,7 @@ static char gLastError[2000];
 
 #if defined(__APPLE__) || defined(__linux__) || defined(MOZ_CALLGRIND)
 static void
-#ifdef __GNUC__
-__attribute__((format(printf,1,2)))
-#endif
+MOZ_FORMAT_PRINTF(1, 2)
 UnsafeError(const char* format, ...)
 {
     va_list args;
diff --git a/js/src/devtools/gctrace/gcstats.cpp b/js/src/devtools/gctrace/gcstats.cpp
index 9b7d22247aef..865e65839dea 100644
--- a/js/src/devtools/gctrace/gcstats.cpp
+++ b/js/src/devtools/gctrace/gcstats.cpp
@@ -165,6 +165,7 @@ Array<Array<uint64_t, MaxLifetimeBins>, MaxClasses> finalizedHeapObjectCountByCl
 std::vector<Array<Array<uint64_t, MaxLifetimeBins>, HeapKinds> > objectCountByTypeHeapAndLifetime;
 
 static void
+MOZ_FORMAT_PRINTF(1, 2)
 die(const char* format, ...)
 {
     va_list va;
diff --git a/js/src/gc/Verifier.cpp b/js/src/gc/Verifier.cpp
index 416ec000c316..4b6138b7661b 100644
--- a/js/src/gc/Verifier.cpp
+++ b/js/src/gc/Verifier.cpp
@@ -535,7 +535,7 @@ CheckHeapTracer::check(AutoLockForExclusiveAccess& lock)
         return;
 
     if (failures) {
-        fprintf(stderr, "Heap check: %zu failure(s) out of %" PRIu32 " pointers checked\n",
+        fprintf(stderr, "Heap check: %" PRIuSIZE " failure(s) out of %" PRIu32 " pointers checked\n",
                 failures, visited.count());
     }
     MOZ_RELEASE_ASSERT(failures == 0);
diff --git a/js/src/irregexp/RegExpEngine.cpp b/js/src/irregexp/RegExpEngine.cpp
index 623525d2215a..bc556b4a1ef2 100644
--- a/js/src/irregexp/RegExpEngine.cpp
+++ b/js/src/irregexp/RegExpEngine.cpp
@@ -1872,7 +1872,7 @@ irregexp::CompilePattern(JSContext* cx, RegExpShared* shared, RegExpCompileData*
     Analysis analysis(cx, ignore_case, is_ascii, unicode);
     analysis.EnsureAnalyzed(node);
     if (analysis.has_failed()) {
-        JS_ReportErrorASCII(cx, analysis.errorMessage());
+        JS_ReportErrorASCII(cx, "%s", analysis.errorMessage());
         return RegExpCode();
     }
 
diff --git a/js/src/jit/BacktrackingAllocator.cpp b/js/src/jit/BacktrackingAllocator.cpp
index 8d2bca22bf67..bb5dfac3624f 100644
--- a/js/src/jit/BacktrackingAllocator.cpp
+++ b/js/src/jit/BacktrackingAllocator.cpp
@@ -1245,7 +1245,7 @@ bool
 BacktrackingAllocator::processBundle(MIRGenerator* mir, LiveBundle* bundle)
 {
     if (JitSpewEnabled(JitSpew_RegAlloc)) {
-        JitSpew(JitSpew_RegAlloc, "Allocating %s [priority %lu] [weight %lu]",
+        JitSpew(JitSpew_RegAlloc, "Allocating %s [priority %" PRIuSIZE "] [weight %" PRIuSIZE "]",
                 bundle->toString().get(), computePriority(bundle), computeSpillWeight(bundle));
     }
 
@@ -1437,13 +1437,13 @@ BacktrackingAllocator::tryAllocateRegister(PhysicalRegister& r, LiveBundle* bund
         if (JitSpewEnabled(JitSpew_RegAlloc)) {
             if (aliasedConflicting.length() == 1) {
                 LiveBundle* existing = aliasedConflicting[0];
-                JitSpew(JitSpew_RegAlloc, "  %s collides with %s [weight %lu]",
+                JitSpew(JitSpew_RegAlloc, "  %s collides with %s [weight %" PRIuSIZE "]",
                         r.reg.name(), existing->toString().get(), computeSpillWeight(existing));
             } else {
                 JitSpew(JitSpew_RegAlloc, "  %s collides with the following", r.reg.name());
                 for (size_t i = 0; i < aliasedConflicting.length(); i++) {
                     LiveBundle* existing = aliasedConflicting[i];
-                    JitSpew(JitSpew_RegAlloc, "      %s [weight %lu]",
+                    JitSpew(JitSpew_RegAlloc, "      %s [weight %" PRIuSIZE "]",
                             existing->toString().get(), computeSpillWeight(existing));
                 }
             }
@@ -1482,7 +1482,7 @@ bool
 BacktrackingAllocator::evictBundle(LiveBundle* bundle)
 {
     if (JitSpewEnabled(JitSpew_RegAlloc)) {
-        JitSpew(JitSpew_RegAlloc, "  Evicting %s [priority %lu] [weight %lu]",
+        JitSpew(JitSpew_RegAlloc, "  Evicting %s [priority %" PRIuSIZE "] [weight %" PRIuSIZE "]",
                 bundle->toString().get(), computePriority(bundle), computeSpillWeight(bundle));
     }
 
@@ -2296,7 +2296,8 @@ LiveBundle::toString() const
 {
     AutoEnterOOMUnsafeRegion oomUnsafe;
 
-    char *buf = JS_smprintf("");
+    // Suppress -Wformat warning.
+    char *buf = JS_smprintf("%s", "");
 
     for (LiveRange::BundleLinkIterator iter = rangesBegin(); buf && iter; iter++) {
         buf = JS_sprintf_append(buf, "%s %s",
diff --git a/js/src/jit/BaselineBailouts.cpp b/js/src/jit/BaselineBailouts.cpp
index 4c990b61de55..0b081c265483 100644
--- a/js/src/jit/BaselineBailouts.cpp
+++ b/js/src/jit/BaselineBailouts.cpp
@@ -230,11 +230,11 @@ struct BaselineStackBuilder
         if (info) {
             if (sizeof(size_t) == 4) {
                 JitSpew(JitSpew_BaselineBailouts,
-                        "      WRITE_WRD %p/%p %-15s %08x",
+                        "      WRITE_WRD %p/%p %-15s %08" PRIxSIZE,
                         header_->copyStackBottom, virtualPointerAtStackOffset(0), info, w);
             } else {
                 JitSpew(JitSpew_BaselineBailouts,
-                        "      WRITE_WRD %p/%p %-15s %016llx",
+                        "      WRITE_WRD %p/%p %-15s %016" PRIxSIZE,
                         header_->copyStackBottom, virtualPointerAtStackOffset(0), info, w);
             }
         }
@@ -246,7 +246,7 @@ struct BaselineStackBuilder
             return false;
         if (info) {
             JitSpew(JitSpew_BaselineBailouts,
-                    "      WRITE_VAL %p/%p %-15s %016llx",
+                    "      WRITE_VAL %p/%p %-15s %016" PRIx64,
                     header_->copyStackBottom, virtualPointerAtStackOffset(0), info,
                     *((uint64_t*) &val));
         }
@@ -637,7 +637,7 @@ InitFromBailout(JSContext* cx, HandleScript caller, jsbytecode* callerPC,
     // |  ReturnAddr   | <-- return into main jitcode after IC
     // +===============+
 
-    JitSpew(JitSpew_BaselineBailouts, "      Unpacking %s:%d", script->filename(), script->lineno());
+    JitSpew(JitSpew_BaselineBailouts, "      Unpacking %s:%" PRIuSIZE, script->filename(), script->lineno());
     JitSpew(JitSpew_BaselineBailouts, "      [BASELINE-JS FRAME]");
 
     // Calculate and write the previous frame pointer value.
@@ -749,7 +749,7 @@ InitFromBailout(JSContext* cx, HandleScript caller, jsbytecode* callerPC,
     }
     JitSpew(JitSpew_BaselineBailouts, "      EnvChain=%p", envChain);
     blFrame->setEnvironmentChain(envChain);
-    JitSpew(JitSpew_BaselineBailouts, "      ReturnValue=%016llx", *((uint64_t*) &returnValue));
+    JitSpew(JitSpew_BaselineBailouts, "      ReturnValue=%016" PRIx64, *((uint64_t*) &returnValue));
     blFrame->setReturnValue(returnValue);
 
     // Do not need to initialize scratchValue field in BaselineFrame.
@@ -764,13 +764,13 @@ InitFromBailout(JSContext* cx, HandleScript caller, jsbytecode* callerPC,
         // in the calling frame.
         Value thisv = iter.read();
         JitSpew(JitSpew_BaselineBailouts, "      Is function!");
-        JitSpew(JitSpew_BaselineBailouts, "      thisv=%016llx", *((uint64_t*) &thisv));
+        JitSpew(JitSpew_BaselineBailouts, "      thisv=%016" PRIx64, *((uint64_t*) &thisv));
 
         size_t thisvOffset = builder.framePushed() + JitFrameLayout::offsetOfThis();
         builder.valuePointerAtStackOffset(thisvOffset).set(thisv);
 
         MOZ_ASSERT(iter.numAllocations() >= CountArgSlots(script, fun));
-        JitSpew(JitSpew_BaselineBailouts, "      frame slots %u, nargs %u, nfixed %u",
+        JitSpew(JitSpew_BaselineBailouts, "      frame slots %u, nargs %" PRIuSIZE ", nfixed %" PRIuSIZE,
                 iter.numAllocations(), fun->nargs(), script->nfixed());
 
         if (!callerPC) {
@@ -786,7 +786,7 @@ InitFromBailout(JSContext* cx, HandleScript caller, jsbytecode* callerPC,
 
         for (uint32_t i = 0; i < fun->nargs(); i++) {
             Value arg = iter.read();
-            JitSpew(JitSpew_BaselineBailouts, "      arg %d = %016llx",
+            JitSpew(JitSpew_BaselineBailouts, "      arg %d = %016" PRIx64,
                         (int) i, *((uint64_t*) &arg));
             if (callerPC) {
                 size_t argOffset = builder.framePushed() + JitFrameLayout::offsetOfActualArg(i);
@@ -1314,7 +1314,7 @@ InitFromBailout(JSContext* cx, HandleScript caller, jsbytecode* callerPC,
         return false;
 
     // Push callee token (must be a JS Function)
-    JitSpew(JitSpew_BaselineBailouts, "      Callee = %016llx", callee.asRawBits());
+    JitSpew(JitSpew_BaselineBailouts, "      Callee = %016" PRIx64, callee.asRawBits());
 
     JSFunction* calleeFun = &callee.toObject().as<JSFunction>();
     if (!builder.writePtr(CalleeToToken(calleeFun, JSOp(*pc) == JSOP_NEW), "CalleeToken"))
@@ -1494,7 +1494,7 @@ jit::BailoutIonToBaseline(JSContext* cx, JitActivation* activation, JitFrameIter
     //      |    |||||      |
     //      +---------------+
 
-    JitSpew(JitSpew_BaselineBailouts, "Bailing to baseline %s:%u (IonScript=%p) (FrameType=%d)",
+    JitSpew(JitSpew_BaselineBailouts, "Bailing to baseline %s:%" PRIuSIZE " (IonScript=%p) (FrameType=%d)",
             iter.script()->filename(), iter.script()->lineno(), (void*) iter.ionScript(),
             (int) prevFrameType);
 
@@ -1514,7 +1514,7 @@ jit::BailoutIonToBaseline(JSContext* cx, JitActivation* activation, JitFrameIter
         propagatingExceptionForDebugMode = false;
     }
 
-    JitSpew(JitSpew_BaselineBailouts, "  Reading from snapshot offset %u size %u",
+    JitSpew(JitSpew_BaselineBailouts, "  Reading from snapshot offset %u size %" PRIuSIZE,
             iter.snapshotOffset(), iter.ionScript()->snapshotsListSize());
 
     if (!excInfo)
@@ -1540,7 +1540,7 @@ jit::BailoutIonToBaseline(JSContext* cx, JitActivation* activation, JitFrameIter
     RootedFunction callee(cx, iter.maybeCallee());
     RootedScript scr(cx, iter.script());
     if (callee) {
-        JitSpew(JitSpew_BaselineBailouts, "  Callee function (%s:%u)",
+        JitSpew(JitSpew_BaselineBailouts, "  Callee function (%s:%" PRIuSIZE ")",
                 scr->filename(), scr->lineno());
     } else {
         JitSpew(JitSpew_BaselineBailouts, "  No callee!");
@@ -1575,7 +1575,7 @@ jit::BailoutIonToBaseline(JSContext* cx, JitActivation* activation, JitFrameIter
             TraceLogStartEvent(logger, TraceLogger_Baseline);
         }
 
-        JitSpew(JitSpew_BaselineBailouts, "    FrameNo %d", frameNo);
+        JitSpew(JitSpew_BaselineBailouts, "    FrameNo %" PRIuSIZE, frameNo);
 
         // If we are bailing out to a catch or finally block in this frame,
         // pass excInfo to InitFromBailout and don't unpack any other frames.
@@ -1671,7 +1671,7 @@ InvalidateAfterBailout(JSContext* cx, HandleScript outerScript, const char* reas
 static void
 HandleBoundsCheckFailure(JSContext* cx, HandleScript outerScript, HandleScript innerScript)
 {
-    JitSpew(JitSpew_IonBailouts, "Bounds check failure %s:%d, inlined into %s:%d",
+    JitSpew(JitSpew_IonBailouts, "Bounds check failure %s:%" PRIuSIZE ", inlined into %s:%" PRIuSIZE,
             innerScript->filename(), innerScript->lineno(),
             outerScript->filename(), outerScript->lineno());
 
@@ -1686,7 +1686,7 @@ HandleBoundsCheckFailure(JSContext* cx, HandleScript outerScript, HandleScript i
 static void
 HandleShapeGuardFailure(JSContext* cx, HandleScript outerScript, HandleScript innerScript)
 {
-    JitSpew(JitSpew_IonBailouts, "Shape guard failure %s:%d, inlined into %s:%d",
+    JitSpew(JitSpew_IonBailouts, "Shape guard failure %s:%" PRIuSIZE ", inlined into %s:%" PRIuSIZE,
             innerScript->filename(), innerScript->lineno(),
             outerScript->filename(), outerScript->lineno());
 
@@ -1701,7 +1701,7 @@ HandleShapeGuardFailure(JSContext* cx, HandleScript outerScript, HandleScript in
 static void
 HandleBaselineInfoBailout(JSContext* cx, HandleScript outerScript, HandleScript innerScript)
 {
-    JitSpew(JitSpew_IonBailouts, "Baseline info failure %s:%d, inlined into %s:%d",
+    JitSpew(JitSpew_IonBailouts, "Baseline info failure %s:%" PRIuSIZE ", inlined into %s:%" PRIuSIZE,
             innerScript->filename(), innerScript->lineno(),
             outerScript->filename(), outerScript->lineno());
 
@@ -1711,7 +1711,7 @@ HandleBaselineInfoBailout(JSContext* cx, HandleScript outerScript, HandleScript
 static void
 HandleLexicalCheckFailure(JSContext* cx, HandleScript outerScript, HandleScript innerScript)
 {
-    JitSpew(JitSpew_IonBailouts, "Lexical check failure %s:%d, inlined into %s:%d",
+    JitSpew(JitSpew_IonBailouts, "Lexical check failure %s:%" PRIuSIZE ", inlined into %s:%" PRIuSIZE,
             innerScript->filename(), innerScript->lineno(),
             outerScript->filename(), outerScript->lineno());
 
@@ -1754,7 +1754,7 @@ CopyFromRematerializedFrame(JSContext* cx, JitActivation* act, uint8_t* fp, size
         frame->setHasCachedSavedFrame();
 
     JitSpew(JitSpew_BaselineBailouts,
-            "  Copied from rematerialized frame at (%p,%u)",
+            "  Copied from rematerialized frame at (%p,%" PRIuSIZE ")",
             fp, inlineDepth);
 
     // Propagate the debuggee frame flag. For the case where the Debugger did
@@ -1891,7 +1891,7 @@ jit::FinishBailoutToBaseline(BaselineBailoutInfo* bailoutInfo)
     }
 
     JitSpew(JitSpew_BaselineBailouts,
-            "  Restored outerScript=(%s:%u,%u) innerScript=(%s:%u,%u) (bailoutKind=%u)",
+            "  Restored outerScript=(%s:%" PRIuSIZE ",%u) innerScript=(%s:%" PRIuSIZE ",%u) (bailoutKind=%u)",
             outerScript->filename(), outerScript->lineno(), outerScript->getWarmUpCount(),
             innerScript->filename(), innerScript->lineno(), innerScript->getWarmUpCount(),
             (unsigned) bailoutKind);
diff --git a/js/src/jit/BaselineCompiler.cpp b/js/src/jit/BaselineCompiler.cpp
index 5c9174655a9a..846a6cd3c816 100644
--- a/js/src/jit/BaselineCompiler.cpp
+++ b/js/src/jit/BaselineCompiler.cpp
@@ -7,6 +7,7 @@
 #include "jit/BaselineCompiler.h"
 
 #include "mozilla/Casting.h"
+#include "mozilla/SizePrintfMacros.h"
 
 #include "jit/BaselineIC.h"
 #include "jit/BaselineJIT.h"
@@ -82,10 +83,10 @@ BaselineCompiler::addPCMappingEntry(bool addIndexEntry)
 MethodStatus
 BaselineCompiler::compile()
 {
-    JitSpew(JitSpew_BaselineScripts, "Baseline compiling script %s:%d (%p)",
+    JitSpew(JitSpew_BaselineScripts, "Baseline compiling script %s:%" PRIuSIZE " (%p)",
             script->filename(), script->lineno(), script);
 
-    JitSpew(JitSpew_Codegen, "# Emitting baseline code for script %s:%d",
+    JitSpew(JitSpew_Codegen, "# Emitting baseline code for script %s:%" PRIuSIZE,
             script->filename(), script->lineno());
 
     TraceLoggerThread* logger = TraceLoggerForMainThread(cx->runtime());
@@ -217,7 +218,7 @@ BaselineCompiler::compile()
     baselineScript->setMethod(code);
     baselineScript->setTemplateEnvironment(templateEnv);
 
-    JitSpew(JitSpew_BaselineScripts, "Created BaselineScript %p (raw %p) for %s:%d",
+    JitSpew(JitSpew_BaselineScripts, "Created BaselineScript %p (raw %p) for %s:%" PRIuSIZE,
             (void*) baselineScript.get(), (void*) code->raw(),
             script->filename(), script->lineno());
 
@@ -279,7 +280,7 @@ BaselineCompiler::compile()
     // Always register a native => bytecode mapping entry, since profiler can be
     // turned on with baseline jitcode on stack, and baseline jitcode cannot be invalidated.
     {
-        JitSpew(JitSpew_Profiling, "Added JitcodeGlobalEntry for baseline script %s:%d (%p)",
+        JitSpew(JitSpew_Profiling, "Added JitcodeGlobalEntry for baseline script %s:%" PRIuSIZE " (%p)",
                     script->filename(), script->lineno(), baselineScript.get());
 
         // Generate profiling string.
diff --git a/js/src/jit/BaselineDebugModeOSR.cpp b/js/src/jit/BaselineDebugModeOSR.cpp
index 889f44dc9b70..8b937ee24591 100644
--- a/js/src/jit/BaselineDebugModeOSR.cpp
+++ b/js/src/jit/BaselineDebugModeOSR.cpp
@@ -7,6 +7,7 @@
 #include "jit/BaselineDebugModeOSR.h"
 
 #include "mozilla/DebugOnly.h"
+#include "mozilla/SizePrintfMacros.h"
 
 #include "jit/BaselineIC.h"
 #include "jit/JitcodeMap.h"
@@ -322,7 +323,7 @@ SpewPatchBaselineFrame(uint8_t* oldReturnAddress, uint8_t* newReturnAddress,
                        JSScript* script, ICEntry::Kind frameKind, jsbytecode* pc)
 {
     JitSpew(JitSpew_BaselineDebugModeOSR,
-            "Patch return %p -> %p on BaselineJS frame (%s:%d) from %s at %s",
+            "Patch return %p -> %p on BaselineJS frame (%s:%" PRIuSIZE ") from %s at %s",
             oldReturnAddress, newReturnAddress, script->filename(), script->lineno(),
             ICEntryKindToString(frameKind), CodeName[(JSOp)*pc]);
 }
@@ -332,7 +333,7 @@ SpewPatchBaselineFrameFromExceptionHandler(uint8_t* oldReturnAddress, uint8_t* n
                                            JSScript* script, jsbytecode* pc)
 {
     JitSpew(JitSpew_BaselineDebugModeOSR,
-            "Patch return %p -> %p on BaselineJS frame (%s:%d) from exception handler at %s",
+            "Patch return %p -> %p on BaselineJS frame (%s:%" PRIuSIZE ") from exception handler at %s",
             oldReturnAddress, newReturnAddress, script->filename(), script->lineno(),
             CodeName[(JSOp)*pc]);
 }
@@ -667,7 +668,7 @@ RecompileBaselineScriptForDebugMode(JSContext* cx, JSScript* script,
     if (oldBaselineScript->hasDebugInstrumentation() == observing)
         return true;
 
-    JitSpew(JitSpew_BaselineDebugModeOSR, "Recompiling (%s:%d) for %s",
+    JitSpew(JitSpew_BaselineDebugModeOSR, "Recompiling (%s:%" PRIuSIZE ") for %s",
             script->filename(), script->lineno(), observing ? "DEBUGGING" : "NORMAL EXECUTION");
 
     script->setBaselineScript(cx->runtime(), nullptr);
diff --git a/js/src/jit/BaselineIC.cpp b/js/src/jit/BaselineIC.cpp
index 5835283268d4..4f43c18989d0 100644
--- a/js/src/jit/BaselineIC.cpp
+++ b/js/src/jit/BaselineIC.cpp
@@ -2586,7 +2586,7 @@ DoSetElemFallback(JSContext* cx, BaselineFrame* frame, ICSetElem_Fallback* stub_
             {
                 JitSpew(JitSpew_BaselineIC,
                         "  Generating SetElem_DenseOrUnboxedArrayAdd stub "
-                        "(shape=%p, group=%p, protoDepth=%u)",
+                        "(shape=%p, group=%p, protoDepth=%" PRIuSIZE ")",
                         shape.get(), group.get(), protoDepth);
                 ICSetElemDenseOrUnboxedArrayAddCompiler compiler(cx, obj, protoDepth);
                 ICUpdatedStub* newStub = compiler.getStub(compiler.getStubSpace(outerScript));
diff --git a/js/src/jit/CodeGenerator.cpp b/js/src/jit/CodeGenerator.cpp
index ff10782acef0..9e55d5bb42e3 100644
--- a/js/src/jit/CodeGenerator.cpp
+++ b/js/src/jit/CodeGenerator.cpp
@@ -9244,7 +9244,7 @@ CodeGenerator::generateWasm(wasm::SigIdDesc sigId, wasm::TrapOffset trapOffset,
 bool
 CodeGenerator::generate()
 {
-    JitSpew(JitSpew_Codegen, "# Emitting code for script %s:%d",
+    JitSpew(JitSpew_Codegen, "# Emitting code for script %s:%" PRIuSIZE,
             gen->info().script()->filename(),
             gen->info().script()->lineno());
 
diff --git a/js/src/jit/FlowAliasAnalysis.cpp b/js/src/jit/FlowAliasAnalysis.cpp
index e237163bb7f8..2b88e36785af 100644
--- a/js/src/jit/FlowAliasAnalysis.cpp
+++ b/js/src/jit/FlowAliasAnalysis.cpp
@@ -402,7 +402,7 @@ DumpImprovement(MDefinition *load, MDefinitionVector& input, MDefinitionVector&
     if (JitSpewEnabled(JitSpew_Alias)) {
         Fprinter &print = JitSpewPrinter();
         JitSpewHeader(JitSpew_Alias);
-        print.printf("   Improve dependency from ", load->id());
+        print.printf("   Improve dependency from %d", load->id());
         DumpStoreList(input);
         print.printf(" to ");
         DumpStoreList(output);
diff --git a/js/src/jit/Ion.cpp b/js/src/jit/Ion.cpp
index 945947e77308..cacd6e181e7a 100644
--- a/js/src/jit/Ion.cpp
+++ b/js/src/jit/Ion.cpp
@@ -6,6 +6,7 @@
 
 #include "jit/Ion.h"
 
+#include "mozilla/IntegerPrintfMacros.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/SizePrintfMacros.h"
 #include "mozilla/ThreadLocal.h"
@@ -2136,7 +2137,7 @@ TrackIonAbort(JSContext* cx, JSScript* script, jsbytecode* pc, const char* messa
 static void
 TrackAndSpewIonAbort(JSContext* cx, JSScript* script, const char* message)
 {
-    JitSpew(JitSpew_IonAbort, message);
+    JitSpew(JitSpew_IonAbort, "%s", message);
     TrackIonAbort(cx, script, script->code(), message);
 }
 
@@ -2395,7 +2396,7 @@ CheckScriptSize(JSContext* cx, JSScript* script)
         numLocalsAndArgs > MAX_MAIN_THREAD_LOCALS_AND_ARGS)
     {
         if (!OffThreadCompilationAvailable(cx)) {
-            JitSpew(JitSpew_IonAbort, "Script too large (%u bytes) (%u locals/args)",
+            JitSpew(JitSpew_IonAbort, "Script too large (%" PRIuSIZE " bytes) (%u locals/args)",
                     script->length(), numLocalsAndArgs);
             TrackIonAbort(cx, script, script->code(), "too large");
             return Method_CantCompile;
@@ -3012,7 +3013,7 @@ InvalidateActivation(FreeOp* fop, const JitActivationIterator& activations, bool
 #ifdef JS_JITSPEW
         switch (it.type()) {
           case JitFrame_Exit:
-            JitSpew(JitSpew_IonInvalidate, "#%d exit frame @ %p", frameno, it.fp());
+            JitSpew(JitSpew_IonInvalidate, "#%" PRIuSIZE " exit frame @ %p", frameno, it.fp());
             break;
           case JitFrame_BaselineJS:
           case JitFrame_IonJS:
@@ -3027,26 +3028,26 @@ InvalidateActivation(FreeOp* fop, const JitActivationIterator& activations, bool
             else if (it.isBailoutJS())
                 type = "Bailing";
             JitSpew(JitSpew_IonInvalidate,
-                    "#%d %s JS frame @ %p, %s:%" PRIuSIZE " (fun: %p, script: %p, pc %p)",
+                    "#%" PRIuSIZE " %s JS frame @ %p, %s:%" PRIuSIZE " (fun: %p, script: %p, pc %p)",
                     frameno, type, it.fp(), it.script()->maybeForwardedFilename(),
                     it.script()->lineno(), it.maybeCallee(), (JSScript*)it.script(),
                     it.returnAddressToFp());
             break;
           }
           case JitFrame_IonStub:
-            JitSpew(JitSpew_IonInvalidate, "#%d ion stub frame @ %p", frameno, it.fp());
+            JitSpew(JitSpew_IonInvalidate, "#%" PRIuSIZE " ion stub frame @ %p", frameno, it.fp());
             break;
           case JitFrame_BaselineStub:
-            JitSpew(JitSpew_IonInvalidate, "#%d baseline stub frame @ %p", frameno, it.fp());
+            JitSpew(JitSpew_IonInvalidate, "#%" PRIuSIZE " baseline stub frame @ %p", frameno, it.fp());
             break;
           case JitFrame_Rectifier:
-            JitSpew(JitSpew_IonInvalidate, "#%d rectifier frame @ %p", frameno, it.fp());
+            JitSpew(JitSpew_IonInvalidate, "#%" PRIuSIZE " rectifier frame @ %p", frameno, it.fp());
             break;
           case JitFrame_IonAccessorIC:
-            JitSpew(JitSpew_IonInvalidate, "#%d ion IC getter/setter frame @ %p", frameno, it.fp());
+            JitSpew(JitSpew_IonInvalidate, "#%" PRIuSIZE " ion IC getter/setter frame @ %p", frameno, it.fp());
             break;
           case JitFrame_Entry:
-            JitSpew(JitSpew_IonInvalidate, "#%d entry frame @ %p", frameno, it.fp());
+            JitSpew(JitSpew_IonInvalidate, "#%" PRIuSIZE " entry frame @ %p", frameno, it.fp());
             break;
         }
 #endif // JS_JITSPEW
@@ -3141,7 +3142,7 @@ InvalidateActivation(FreeOp* fop, const JitActivationIterator& activations, bool
         CodeLocationLabel osiPatchPoint = SafepointReader::InvalidationPatchPoint(ionScript, si);
         CodeLocationLabel invalidateEpilogue(ionCode, CodeOffset(ionScript->invalidateEpilogueOffset()));
 
-        JitSpew(JitSpew_IonInvalidate, "   ! Invalidate ionScript %p (inv count %u) -> patching osipoint %p",
+        JitSpew(JitSpew_IonInvalidate, "   ! Invalidate ionScript %p (inv count %" PRIuSIZE ") -> patching osipoint %p",
                 ionScript, ionScript->invalidationCount(), (void*) osiPatchPoint.raw());
         Assembler::PatchWrite_NearCall(osiPatchPoint, invalidateEpilogue);
     }
@@ -3358,7 +3359,7 @@ AutoFlushICache::setRange(uintptr_t start, size_t len)
     AutoFlushICache* afc = TlsPerThreadData.get()->PerThreadData::autoFlushICache();
     MOZ_ASSERT(afc);
     MOZ_ASSERT(!afc->start_);
-    JitSpewCont(JitSpew_CacheFlush, "(%x %x):", start, len);
+    JitSpewCont(JitSpew_CacheFlush, "(%" PRIxPTR " %" PRIxSIZE "):", start, len);
 
     uintptr_t stop = start + len;
     afc->start_ = start;
diff --git a/js/src/jit/IonAnalysis.cpp b/js/src/jit/IonAnalysis.cpp
index 5a2d7b14d717..ffb7a6877332 100644
--- a/js/src/jit/IonAnalysis.cpp
+++ b/js/src/jit/IonAnalysis.cpp
@@ -6,6 +6,8 @@
 
 #include "jit/IonAnalysis.h"
 
+#include "mozilla/SizePrintfMacros.h"
+
 #include "jit/AliasAnalysis.h"
 #include "jit/BaselineInspector.h"
 #include "jit/BaselineJIT.h"
@@ -445,9 +447,10 @@ jit::PruneUnusedBranches(MIRGenerator* mir, MIRGraph& graph)
                 shouldBailout = false;
 
             JitSpew(JitSpew_Prune, "info: block %d,"
-                    " predCount: %lu, domInst: %lu, span: %lu, effectful: %lu, "
-                    " isLoopExit: %s, numSuccessorsOfPred: %lu."
-                    " (score: %lu, shouldBailout: %s)",
+                    " predCount: %" PRIuSIZE ", domInst: %" PRIuSIZE
+                    ", span: %" PRIuSIZE ", effectful: %" PRIuSIZE ", "
+                    " isLoopExit: %s, numSuccessorsOfPred: %" PRIuSIZE "."
+                    " (score: %" PRIuSIZE ", shouldBailout: %s)",
                     block->id(), predCount, numDominatedInst, branchSpan, numEffectfulInst,
                     isLoopExit ? "true" : "false", numSuccessorsOfPreds,
                     score, shouldBailout ? "true" : "false");
diff --git a/js/src/jit/IonBuilder.h b/js/src/jit/IonBuilder.h
index 42797a84c8bd..868d9e8e497f 100644
--- a/js/src/jit/IonBuilder.h
+++ b/js/src/jit/IonBuilder.h
@@ -229,7 +229,7 @@ class IonBuilder
     MOZ_MUST_USE bool inspectOpcode(JSOp op);
     uint32_t readIndex(jsbytecode* pc);
     JSAtom* readAtom(jsbytecode* pc);
-    bool abort(const char* message, ...);
+    bool abort(const char* message, ...) MOZ_FORMAT_PRINTF(2, 3);
     void trackActionableAbort(const char* message);
     void spew(const char* message);
 
diff --git a/js/src/jit/JSONSpewer.cpp b/js/src/jit/JSONSpewer.cpp
index d6105f498bab..330b419f5774 100644
--- a/js/src/jit/JSONSpewer.cpp
+++ b/js/src/jit/JSONSpewer.cpp
@@ -8,6 +8,8 @@
 
 #include "jit/JSONSpewer.h"
 
+#include "mozilla/SizePrintfMacros.h"
+
 #include <stdarg.h>
 
 #include "jit/BacktrackingAllocator.h"
@@ -146,7 +148,7 @@ JSONSpewer::beginFunction(JSScript* script)
 {
     beginObject();
     if (script)
-        stringProperty("name", "%s:%d", script->filename(), script->lineno());
+        stringProperty("name", "%s:%" PRIuSIZE, script->filename(), script->lineno());
     else
         stringProperty("name", "asm.js compilation");
     beginListProperty("passes");
@@ -156,7 +158,7 @@ void
 JSONSpewer::beginPass(const char* pass)
 {
     beginObject();
-    stringProperty("name", pass);
+    stringProperty("name", "%s", pass);
 }
 
 void
diff --git a/js/src/jit/JSONSpewer.h b/js/src/jit/JSONSpewer.h
index f4172c6b46ed..02f449c7ab04 100644
--- a/js/src/jit/JSONSpewer.h
+++ b/js/src/jit/JSONSpewer.h
@@ -36,8 +36,8 @@ class JSONSpewer
     void beginObject();
     void beginObjectProperty(const char* name);
     void beginListProperty(const char* name);
-    void stringValue(const char* format, ...);
-    void stringProperty(const char* name, const char* format, ...);
+    void stringValue(const char* format, ...) MOZ_FORMAT_PRINTF(2, 3);
+    void stringProperty(const char* name, const char* format, ...) MOZ_FORMAT_PRINTF(3, 4);
     void beginStringProperty(const char* name);
     void endStringProperty();
     void integerValue(int value);
diff --git a/js/src/jit/JitSpewer.h b/js/src/jit/JitSpewer.h
index 024e7d5a1ff8..a44eec4662f9 100644
--- a/js/src/jit/JitSpewer.h
+++ b/js/src/jit/JitSpewer.h
@@ -172,9 +172,9 @@ class JitSpewIndent
     ~JitSpewIndent();
 };
 
-void JitSpew(JitSpewChannel channel, const char* fmt, ...);
-void JitSpewStart(JitSpewChannel channel, const char* fmt, ...);
-void JitSpewCont(JitSpewChannel channel, const char* fmt, ...);
+void JitSpew(JitSpewChannel channel, const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
+void JitSpewStart(JitSpewChannel channel, const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
+void JitSpewCont(JitSpewChannel channel, const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
 void JitSpewFin(JitSpewChannel channel);
 void JitSpewHeader(JitSpewChannel channel);
 bool JitSpewEnabled(JitSpewChannel channel);
diff --git a/js/src/jit/MIR.cpp b/js/src/jit/MIR.cpp
index c8c11110d4c8..02ef4ac9b78d 100644
--- a/js/src/jit/MIR.cpp
+++ b/js/src/jit/MIR.cpp
@@ -5162,7 +5162,7 @@ void
 MStoreSlot::printOpcode(GenericPrinter& out) const
 {
     PrintOpcodeName(out, op());
-    out.printf(" ", slot());
+    out.printf(" ");
     getOperand(0)->printName(out);
     out.printf(" %d ", slot());
     getOperand(1)->printName(out);
diff --git a/js/src/jit/MIRGenerator.h b/js/src/jit/MIRGenerator.h
index 2aedc1a924a6..342ff2945431 100644
--- a/js/src/jit/MIRGenerator.h
+++ b/js/src/jit/MIRGenerator.h
@@ -72,7 +72,7 @@ class MIRGenerator
 
     // Set an error state and prints a message. Returns false so errors can be
     // propagated up.
-    bool abort(const char* message, ...);           // always returns false
+    bool abort(const char* message, ...) MOZ_FORMAT_PRINTF(2, 3); // always returns false
     bool abortFmt(const char* message, va_list ap); // always returns false
 
     bool errored() const {
diff --git a/js/src/jit/OptimizationTracking.cpp b/js/src/jit/OptimizationTracking.cpp
index 029b3c082be1..103ee4516113 100644
--- a/js/src/jit/OptimizationTracking.cpp
+++ b/js/src/jit/OptimizationTracking.cpp
@@ -326,7 +326,7 @@ UniqueTrackedOptimizations::sortByFrequency(JSContext* cx)
         MOZ_ASSERT(p);
         p->value().index = sorted_.length();
 
-        JitSpew(JitSpew_OptimizationTracking, "   Entry %u has frequency %u",
+        JitSpew(JitSpew_OptimizationTracking, "   Entry %" PRIuSIZE " has frequency %" PRIu32,
                 sorted_.length(), p->value().frequency);
 
         if (!sorted_.append(entries[i]))
@@ -765,14 +765,14 @@ IonTrackedOptimizationsRegion::WriteRun(CompactBufferWriter& writer,
                                         const UniqueTrackedOptimizations& unique)
 {
     // Write the header, which is the range that this whole run encompasses.
-    JitSpew(JitSpew_OptimizationTracking, "     Header: [%u, %u]",
+    JitSpew(JitSpew_OptimizationTracking, "     Header: [%" PRIuSIZE ", %" PRIuSIZE "]",
             start->startOffset.offset(), (end - 1)->endOffset.offset());
     writer.writeUnsigned(start->startOffset.offset());
     writer.writeUnsigned((end - 1)->endOffset.offset());
 
     // Write the first entry of the run, which is not delta-encoded.
     JitSpew(JitSpew_OptimizationTracking,
-            "     [%6u, %6u]                        vector %3u, offset %4u",
+            "     [%6" PRIuSIZE ", %6" PRIuSIZE "]                        vector %3u, offset %4" PRIuSIZE,
             start->startOffset.offset(), start->endOffset.offset(),
             unique.indexOf(start->optimizations), writer.length());
     uint32_t prevEndOffset = start->endOffset.offset();
@@ -789,7 +789,7 @@ IonTrackedOptimizationsRegion::WriteRun(CompactBufferWriter& writer,
         uint8_t index = unique.indexOf(entry->optimizations);
 
         JitSpew(JitSpew_OptimizationTracking,
-                "     [%6u, %6u] delta [+%5u, +%5u] vector %3u, offset %4u",
+                "     [%6u, %6u] delta [+%5u, +%5u] vector %3u, offset %4" PRIuSIZE,
                 startOffset, endOffset, startDelta, length, index, writer.length());
 
         WriteDelta(writer, startDelta, length, index);
@@ -825,7 +825,7 @@ WriteOffsetsTable(CompactBufferWriter& writer, const Vector<uint32_t, 16>& offse
 
     // Write entry offset table.
     for (size_t i = 0; i < offsets.length(); i++) {
-        JitSpew(JitSpew_OptimizationTracking, "   Entry %u reverse offset %u",
+        JitSpew(JitSpew_OptimizationTracking, "   Entry %" PRIuSIZE " reverse offset %u",
                 i, tableOffset - padding - offsets[i]);
         writer.writeNativeEndianUint32_t(tableOffset - padding - offsets[i]);
     }
@@ -885,7 +885,7 @@ SpewConstructor(TypeSet::Type ty, JSFunction* constructor)
     Maybe<unsigned> lineno;
     InterpretedFunctionFilenameAndLineNumber(constructor, &filename, &lineno);
 
-    JitSpew(JitSpew_OptimizationTracking, "   Unique type %s has constructor %s (%s:%" PRIuSIZE ")",
+    JitSpew(JitSpew_OptimizationTracking, "   Unique type %s has constructor %s (%s:%u)",
             TypeSet::TypeString(ty), buf, filename, lineno.isSome() ? *lineno : 0);
 #endif
 }
@@ -919,7 +919,7 @@ jit::WriteIonTrackedOptimizationsTable(JSContext* cx, CompactBufferWriter& write
     if (JitSpewEnabled(JitSpew_OptimizationTracking)) {
         JitSpewStart(JitSpew_OptimizationTracking, "=> Training data: ");
         for (const NativeToTrackedOptimizations* entry = start; entry != end; entry++) {
-            JitSpewCont(JitSpew_OptimizationTracking, "%u,%u,%u ",
+            JitSpewCont(JitSpew_OptimizationTracking, "%" PRIuSIZE ",%" PRIuSIZE ",%u ",
                         entry->startOffset.offset(), entry->endOffset.offset(),
                         unique.indexOf(entry->optimizations));
         }
@@ -934,7 +934,8 @@ jit::WriteIonTrackedOptimizationsTable(JSContext* cx, CompactBufferWriter& write
     JitSpew(JitSpew_Profiling, "=> Writing regions");
     while (entry != end) {
         uint32_t runLength = IonTrackedOptimizationsRegion::ExpectedRunLength(entry, end);
-        JitSpew(JitSpew_OptimizationTracking, "   Run at entry %u, length %u, offset %u",
+        JitSpew(JitSpew_OptimizationTracking,
+                "   Run at entry %" PRIuSIZE ", length %" PRIu32 ", offset %" PRIuSIZE,
                 entry - start, runLength, writer.length());
 
         if (!offsets.append(writer.length()))
@@ -957,7 +958,7 @@ jit::WriteIonTrackedOptimizationsTable(JSContext* cx, CompactBufferWriter& write
     offsets.clear();
 
     const UniqueTrackedOptimizations::SortedVector& vec = unique.sortedVector();
-    JitSpew(JitSpew_OptimizationTracking, "=> Writing unique optimizations table with %u entr%s",
+    JitSpew(JitSpew_OptimizationTracking, "=> Writing unique optimizations table with %" PRIuSIZE " entr%s",
             vec.length(), vec.length() == 1 ? "y" : "ies");
 
     // Write out type info payloads.
@@ -967,7 +968,8 @@ jit::WriteIonTrackedOptimizationsTable(JSContext* cx, CompactBufferWriter& write
 
     for (const UniqueTrackedOptimizations::SortEntry* p = vec.begin(); p != vec.end(); p++) {
         const TempOptimizationTypeInfoVector* v = p->types;
-        JitSpew(JitSpew_OptimizationTracking, "   Type info entry %u of length %u, offset %u",
+        JitSpew(JitSpew_OptimizationTracking,
+                "   Type info entry %" PRIuSIZE " of length %" PRIuSIZE ", offset %" PRIuSIZE,
                 p - vec.begin(), v->length(), writer.length());
         SpewTempOptimizationTypeInfoVector(v, "  ");
 
@@ -1017,7 +1019,8 @@ jit::WriteIonTrackedOptimizationsTable(JSContext* cx, CompactBufferWriter& write
     // Write out attempts payloads.
     for (const UniqueTrackedOptimizations::SortEntry* p = vec.begin(); p != vec.end(); p++) {
         const TempOptimizationAttemptsVector* v = p->attempts;
-        JitSpew(JitSpew_OptimizationTracking, "   Attempts entry %u of length %u, offset %u",
+        JitSpew(JitSpew_OptimizationTracking,
+                "   Attempts entry %" PRIuSIZE " of length %" PRIuSIZE ", offset %" PRIuSIZE,
                 p - vec.begin(), v->length(), writer.length());
         SpewTempOptimizationAttemptsVector(v, "  ");
 
diff --git a/js/src/jit/Recover.cpp b/js/src/jit/Recover.cpp
index 57577160544f..57d5d18a465b 100644
--- a/js/src/jit/Recover.cpp
+++ b/js/src/jit/Recover.cpp
@@ -6,6 +6,8 @@
 
 #include "jit/Recover.h"
 
+#include "mozilla/SizePrintfMacros.h"
+
 #include "jsapi.h"
 #include "jscntxt.h"
 #include "jsmath.h"
@@ -123,7 +125,7 @@ MResumePoint::writeRecoverData(CompactBufferWriter& writer) const
     uint32_t formalArgs = CountArgSlots(script, fun);
     uint32_t nallocs = formalArgs + script->nfixed() + exprStack;
 
-    JitSpew(JitSpew_IonSnapshots, "Starting frame; implicit %u, formals %u, fixed %u, exprs %u",
+    JitSpew(JitSpew_IonSnapshots, "Starting frame; implicit %u, formals %u, fixed %" PRIuSIZE ", exprs %u",
             implicit, formalArgs - implicit, script->nfixed(), exprStack);
 
     uint32_t pcoff = script->pcToOffset(pc());
diff --git a/js/src/jit/Safepoints.cpp b/js/src/jit/Safepoints.cpp
index c775c7d131c0..b0bb530f9933 100644
--- a/js/src/jit/Safepoints.cpp
+++ b/js/src/jit/Safepoints.cpp
@@ -7,6 +7,7 @@
 #include "jit/Safepoints.h"
 
 #include "mozilla/MathAlgorithms.h"
+#include "mozilla/SizePrintfMacros.h"
 
 #include "jit/BitSet.h"
 #include "jit/JitSpewer.h"
@@ -31,7 +32,7 @@ SafepointWriter::init(TempAllocator& alloc)
 uint32_t
 SafepointWriter::startEntry()
 {
-    JitSpew(JitSpew_Safepoints, "Encoding safepoint (position %d):", stream_.length());
+    JitSpew(JitSpew_Safepoints, "Encoding safepoint (position %" PRIuSIZE "):", stream_.length());
     return uint32_t(stream_.length());
 }
 
diff --git a/js/src/jit/SharedIC.cpp b/js/src/jit/SharedIC.cpp
index 1c227439e349..177f5e8e394e 100644
--- a/js/src/jit/SharedIC.cpp
+++ b/js/src/jit/SharedIC.cpp
@@ -2132,7 +2132,7 @@ UpdateExistingGenerationalDOMProxyStub(ICGetProp_Fallback* stub,
                 // Update generation
                 uint64_t generation = expandoAndGeneration->generation;
                 JitSpew(JitSpew_BaselineIC,
-                        "  Updating existing stub with generation, old value: %i, "
+                        "  Updating existing stub with generation, old value: %" PRIu64 ", "
                         "new value: %" PRIu64 "", updateStub->generation(),
                         generation);
                 updateStub->setGeneration(generation);
diff --git a/js/src/jit/SharedIC.h b/js/src/jit/SharedIC.h
index b8e081688897..42198c89096f 100644
--- a/js/src/jit/SharedIC.h
+++ b/js/src/jit/SharedIC.h
@@ -202,8 +202,10 @@ class ICFallbackStub;
 #undef FORWARD_DECLARE_STUBS
 
 #ifdef JS_JITSPEW
-void FallbackICSpew(JSContext* cx, ICFallbackStub* stub, const char* fmt, ...);
-void TypeFallbackICSpew(JSContext* cx, ICTypeMonitor_Fallback* stub, const char* fmt, ...);
+void FallbackICSpew(JSContext* cx, ICFallbackStub* stub, const char* fmt, ...)
+    MOZ_FORMAT_PRINTF(3, 4);
+void TypeFallbackICSpew(JSContext* cx, ICTypeMonitor_Fallback* stub, const char* fmt, ...)
+    MOZ_FORMAT_PRINTF(3, 4);
 #else
 #define FallbackICSpew(...)
 #define TypeFallbackICSpew(...)
diff --git a/js/src/jit/ValueNumbering.cpp b/js/src/jit/ValueNumbering.cpp
index 2335e5f2044d..5a3115646729 100644
--- a/js/src/jit/ValueNumbering.cpp
+++ b/js/src/jit/ValueNumbering.cpp
@@ -1002,7 +1002,7 @@ ValueNumberer::visitBlock(MBasicBlock* block, const MBasicBlock* dominatorRoot)
 bool
 ValueNumberer::visitDominatorTree(MBasicBlock* dominatorRoot)
 {
-    JitSpew(JitSpew_GVN, "  Visiting dominator tree (with %llu blocks) rooted at block%u%s",
+    JitSpew(JitSpew_GVN, "  Visiting dominator tree (with %" PRIu64 " blocks) rooted at block%u%s",
             uint64_t(dominatorRoot->numDominated()), dominatorRoot->id(),
             dominatorRoot == graph_.entryBlock() ? " (normal entry block)" :
             dominatorRoot == graph_.osrBlock() ? " (OSR entry block)" :
@@ -1228,7 +1228,7 @@ ValueNumberer::run(UpdateAliasAnalysisFlag updateAliasAnalysis)
 {
     updateAliasAnalysis_ = updateAliasAnalysis == UpdateAliasAnalysis;
 
-    JitSpew(JitSpew_GVN, "Running GVN on graph (with %llu blocks)",
+    JitSpew(JitSpew_GVN, "Running GVN on graph (with %" PRIu64 " blocks)",
             uint64_t(graph_.numBlocks()));
 
     // Adding fixup blocks only make sense iff we have a second entry point into
@@ -1288,7 +1288,7 @@ ValueNumberer::run(UpdateAliasAnalysisFlag updateAliasAnalysis)
             break;
         }
 
-        JitSpew(JitSpew_GVN, "Re-running GVN on graph (run %d, now with %llu blocks)",
+        JitSpew(JitSpew_GVN, "Re-running GVN on graph (run %d, now with %" PRIu64 " blocks)",
                 runs, uint64_t(graph_.numBlocks()));
     }
 
diff --git a/js/src/jit/arm/Assembler-arm.h b/js/src/jit/arm/Assembler-arm.h
index 455a3e828515..04813096c044 100644
--- a/js/src/jit/arm/Assembler-arm.h
+++ b/js/src/jit/arm/Assembler-arm.h
@@ -1363,7 +1363,7 @@ class Assembler : public AssemblerShared
     uint32_t spewResolve(Label* l);
     uint32_t spewProbe(Label* l);
     uint32_t spewDefine(Label* l);
-    void spew(const char* fmt, ...);
+    void spew(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
     void spew(const char* fmt, va_list args);
 #endif
 
diff --git a/js/src/jit/arm/disasm/Disasm-arm.cpp b/js/src/jit/arm/disasm/Disasm-arm.cpp
index 1e0cb389387b..8bd7bff0c283 100644
--- a/js/src/jit/arm/disasm/Disasm-arm.cpp
+++ b/js/src/jit/arm/disasm/Disasm-arm.cpp
@@ -43,6 +43,7 @@ namespace disasm {
 
 // Helper function for printing to a Vector.
 static int
+MOZ_FORMAT_PRINTF(2, 3)
 SNPrintF(V8Vector<char> str, const char* format, ...)
 {
     va_list args;
diff --git a/js/src/jit/shared/CodeGenerator-shared.cpp b/js/src/jit/shared/CodeGenerator-shared.cpp
index 30c638edc375..f69cb7449196 100644
--- a/js/src/jit/shared/CodeGenerator-shared.cpp
+++ b/js/src/jit/shared/CodeGenerator-shared.cpp
@@ -7,6 +7,7 @@
 #include "jit/shared/CodeGenerator-shared-inl.h"
 
 #include "mozilla/DebugOnly.h"
+#include "mozilla/SizePrintfMacros.h"
 
 #include "jit/CompactBuffer.h"
 #include "jit/IonCaches.h"
@@ -233,7 +234,7 @@ CodeGeneratorShared::addNativeToBytecodeEntry(const BytecodeSite* site)
         // bytecodeOffset, but the nativeOffset has changed, do nothing.
         // The same site just generated some more code.
         if (lastEntry.tree == tree && lastEntry.pc == pc) {
-            JitSpew(JitSpew_Profiling, " => In-place update [%u-%u]",
+            JitSpew(JitSpew_Profiling, " => In-place update [%" PRIuSIZE "-%" PRIu32 "]",
                     lastEntry.nativeOffset.offset(), nativeOffset);
             return true;
         }
@@ -280,7 +281,7 @@ CodeGeneratorShared::dumpNativeToBytecodeEntries()
 {
 #ifdef JS_JITSPEW
     InlineScriptTree* topTree = gen->info().inlineScriptTree();
-    JitSpewStart(JitSpew_Profiling, "Native To Bytecode Entries for %s:%d\n",
+    JitSpewStart(JitSpew_Profiling, "Native To Bytecode Entries for %s:%" PRIuSIZE "\n",
                  topTree->script()->filename(), topTree->script()->lineno());
     for (unsigned i = 0; i < nativeToBytecodeList_.length(); i++)
         dumpNativeToBytecodeEntry(i);
@@ -303,16 +304,16 @@ CodeGeneratorShared::dumpNativeToBytecodeEntry(uint32_t idx)
         if (nextRef->tree == ref.tree)
             pcDelta = nextRef->pc - ref.pc;
     }
-    JitSpewStart(JitSpew_Profiling, "    %08x [+%-6d] => %-6d [%-4d] {%-10s} (%s:%d",
+    JitSpewStart(JitSpew_Profiling, "    %08" PRIxSIZE " [+%-6d] => %-6ld [%-4d] {%-10s} (%s:%" PRIuSIZE,
                  ref.nativeOffset.offset(),
                  nativeDelta,
-                 ref.pc - script->code(),
+                 (long) (ref.pc - script->code()),
                  pcDelta,
                  CodeName[JSOp(*ref.pc)],
                  script->filename(), script->lineno());
 
     for (tree = tree->caller(); tree; tree = tree->caller()) {
-        JitSpewCont(JitSpew_Profiling, " <= %s:%d", tree->script()->filename(),
+        JitSpewCont(JitSpew_Profiling, " <= %s:%" PRIuSIZE, tree->script()->filename(),
                                                     tree->script()->lineno());
     }
     JitSpewCont(JitSpew_Profiling, ")");
@@ -927,7 +928,7 @@ CodeGeneratorShared::generateCompactTrackedOptimizationsMap(JSContext* cx, JitCo
             "== Compact Native To Optimizations Map [%p-%p] size %u",
             data, data + trackedOptimizationsMapSize_, trackedOptimizationsMapSize_);
     JitSpew(JitSpew_OptimizationTracking,
-            "     with type list of length %u, size %u",
+            "     with type list of length %" PRIuSIZE ", size %" PRIuSIZE,
             allTypes->length(), allTypes->length() * sizeof(IonTrackedTypeWithAddendum));
 
     return true;
diff --git a/js/src/jit/shared/IonAssemblerBufferWithConstantPools.h b/js/src/jit/shared/IonAssemblerBufferWithConstantPools.h
index c6783c61950a..74fa60b12402 100644
--- a/js/src/jit/shared/IonAssemblerBufferWithConstantPools.h
+++ b/js/src/jit/shared/IonAssemblerBufferWithConstantPools.h
@@ -8,6 +8,7 @@
 #define jit_shared_IonAssemblerBufferWithConstantPools_h
 
 #include "mozilla/MathAlgorithms.h"
+#include "mozilla/SizePrintfMacros.h"
 
 #include <algorithm>
 
@@ -792,7 +793,7 @@ struct AssemblerBufferWithConstantPools : public AssemblerBuffer<SliceSize, Inst
             if (numPoolEntries)
                 JitSpew(JitSpew_Pools, "[%d] Inserting pool entry caused a spill", id);
             else
-                JitSpew(JitSpew_Pools, "[%d] Inserting instruction(%d) caused a spill", id,
+                JitSpew(JitSpew_Pools, "[%d] Inserting instruction(%" PRIuSIZE ") caused a spill", id,
                         sizeExcludingCurrentPool());
 
             finishPool();
@@ -863,7 +864,7 @@ struct AssemblerBufferWithConstantPools : public AssemblerBuffer<SliceSize, Inst
         // Now to get an instruction to write.
         PoolEntry retPE;
         if (numPoolEntries) {
-            JitSpew(JitSpew_Pools, "[%d] Entry has index %u, offset %u", id, index,
+            JitSpew(JitSpew_Pools, "[%d] Entry has index %u, offset %" PRIuSIZE, id, index,
                     sizeExcludingCurrentPool());
             Asm::InsertIndexIntoTag(inst, index);
             // Figure out the offset within the pool entries.
@@ -935,8 +936,8 @@ struct AssemblerBufferWithConstantPools : public AssemblerBuffer<SliceSize, Inst
     }
 
     void finishPool() {
-        JitSpew(JitSpew_Pools, "[%d] Attempting to finish pool %d with %d entries.", id,
-                poolInfo_.length(), pool_.numEntries());
+        JitSpew(JitSpew_Pools, "[%d] Attempting to finish pool %" PRIuSIZE " with %u entries.",
+                id, poolInfo_.length(), pool_.numEntries());
 
         if (pool_.numEntries() == 0 && !hasExpirableShortRangeBranches()) {
             // If there is no data in the pool being dumped, don't dump anything.
@@ -1004,7 +1005,7 @@ struct AssemblerBufferWithConstantPools : public AssemblerBuffer<SliceSize, Inst
             // the pool entry that is being loaded.  We need to do a non-trivial
             // amount of math here, since the pool that we've made does not
             // actually reside there in memory.
-            JitSpew(JitSpew_Pools, "[%d] Fixing entry %d offset to %u", id, idx, codeOffset);
+            JitSpew(JitSpew_Pools, "[%d] Fixing entry %d offset to %" PRIuSIZE, id, idx, codeOffset);
             Asm::PatchConstantPoolLoad(inst, (uint8_t*)inst + codeOffset);
         }
 
@@ -1037,7 +1038,7 @@ struct AssemblerBufferWithConstantPools : public AssemblerBuffer<SliceSize, Inst
         // assumed that no pool entries are allocated in a no-pool region and
         // this is asserted when allocating entries.
         if (!hasSpaceForInsts(maxInst, 0)) {
-            JitSpew(JitSpew_Pools, "[%d] No-Pool instruction(%d) caused a spill.", id,
+            JitSpew(JitSpew_Pools, "[%d] No-Pool instruction(%" PRIuSIZE ") caused a spill.", id,
                     sizeExcludingCurrentPool());
             finishPool();
         }
@@ -1077,8 +1078,8 @@ struct AssemblerBufferWithConstantPools : public AssemblerBuffer<SliceSize, Inst
         // dumped at the aligned code position.
         if (!hasSpaceForInsts(requiredFill / InstSize + 1, 0)) {
             // Alignment would cause a pool dump, so dump the pool now.
-            JitSpew(JitSpew_Pools, "[%d] Alignment of %d at %d caused a spill.", id, alignment,
-                    sizeExcludingCurrentPool());
+            JitSpew(JitSpew_Pools, "[%d] Alignment of %d at %" PRIuSIZE " caused a spill.",
+                    id, alignment, sizeExcludingCurrentPool());
             finishPool();
         }
 
diff --git a/js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h b/js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h
index 6243c1822183..8cb5577848e6 100644
--- a/js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h
+++ b/js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h
@@ -186,10 +186,7 @@ namespace jit {
             printer = sp;
         }
 
-        void spew(const char* fmt, ...)
-#ifdef __GNUC__
-            __attribute__ ((format (printf, 2, 3)))
-#endif
+        void spew(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3)
         {
             if (MOZ_UNLIKELY(printer || JitSpewEnabled(JitSpew_Codegen))) {
                 va_list va;
diff --git a/js/src/jsapi-tests/moz.build b/js/src/jsapi-tests/moz.build
index 9081cd68edce..ab42ff3841db 100644
--- a/js/src/jsapi-tests/moz.build
+++ b/js/src/jsapi-tests/moz.build
@@ -73,6 +73,7 @@ UNIFIED_SOURCES += [
     'testParseJSON.cpp',
     'testPersistentRooted.cpp',
     'testPreserveJitCode.cpp',
+    'testPrintf.cpp',
     'testPrivateGCThingValue.cpp',
     'testProfileStrings.cpp',
     'testPropCache.cpp',
@@ -146,7 +147,7 @@ USE_LIBS += [
 OS_LIBS += CONFIG['MOZ_ZLIB_LIBS']
 
 if CONFIG['GNU_CXX']:
-    CXXFLAGS += ['-Wno-shadow']
+    CXXFLAGS += ['-Wno-shadow', '-Werror=format']
 
 # This is intended as a temporary workaround to enable VS2015.
 if CONFIG['_MSC_VER']:
diff --git a/js/src/jsapi-tests/testPrintf.cpp b/js/src/jsapi-tests/testPrintf.cpp
new file mode 100644
index 000000000000..51486856fad8
--- /dev/null
+++ b/js/src/jsapi-tests/testPrintf.cpp
@@ -0,0 +1,71 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/SizePrintfMacros.h"
+
+#include <stdarg.h>
+
+#include "jsprf.h"
+
+#include "jsapi-tests/tests.h"
+
+static bool
+MOZ_FORMAT_PRINTF(2, 3)
+print_one (const char *expect, const char *fmt, ...)
+{
+    va_list ap;
+
+    va_start(ap, fmt);
+    char *output = JS_vsmprintf (fmt, ap);
+    va_end(ap);
+
+    bool result = output && !strcmp(output, expect);
+    JS_smprintf_free(output);
+
+    return result;
+}
+
+static const char *
+zero()
+{
+    return nullptr;
+}
+
+BEGIN_TEST(testPrintf)
+{
+    CHECK(print_one("23", "%d", 23));
+    CHECK(print_one("-1", "%d", -1));
+    CHECK(print_one("23", "%u", 23u));
+    CHECK(print_one("0x17", "0x%x", 23u));
+    CHECK(print_one("0xFF", "0x%X", 255u));
+    CHECK(print_one("027", "0%o", 23u));
+    CHECK(print_one("-1", "%hd", (short) -1));
+    // This could be expanded if need be, it's just convenient to do
+    // it this way.
+    if (sizeof(short) == 2) {
+        CHECK(print_one("8000", "%hx", (unsigned short) 0x8000));
+    }
+    CHECK(print_one("0xf0f0", "0x%lx", 0xf0f0ul));
+    CHECK(print_one("0xF0F0", "0x%llX", 0xf0f0ull));
+    CHECK(print_one("27270", "%zu", (size_t) 27270));
+    CHECK(print_one("27270", "%" PRIuSIZE, (size_t) 27270));
+    CHECK(print_one("hello", "he%so", "ll"));
+    CHECK(print_one("(null)", "%s", zero()));
+    CHECK(print_one("0", "%p", (char *) 0));
+    CHECK(print_one("h", "%c", 'h'));
+    CHECK(print_one("1.500000", "%f", 1.5f));
+    CHECK(print_one("1.5", "%g", 1.5));
+
+    CHECK(print_one("2727", "%" PRIu32, (uint32_t) 2727));
+    CHECK(print_one("aa7", "%" PRIx32, (uint32_t) 2727));
+    CHECK(print_one("2727", "%" PRIu64, (uint64_t) 2727));
+    CHECK(print_one("aa7", "%" PRIx64, (uint64_t) 2727));
+
+    return true;
+}
+END_TEST(testPrintf)
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 9dc247562fbf..fcf94fea486f 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -5199,13 +5199,16 @@ const uint16_t MaxNumErrorArguments = 10;
  * and its arguments.
  */
 extern JS_PUBLIC_API(void)
-JS_ReportErrorASCII(JSContext* cx, const char* format, ...);
+JS_ReportErrorASCII(JSContext* cx, const char* format, ...)
+    MOZ_FORMAT_PRINTF(2, 3);
 
 extern JS_PUBLIC_API(void)
-JS_ReportErrorLatin1(JSContext* cx, const char* format, ...);
+JS_ReportErrorLatin1(JSContext* cx, const char* format, ...)
+    MOZ_FORMAT_PRINTF(2, 3);
 
 extern JS_PUBLIC_API(void)
-JS_ReportErrorUTF8(JSContext* cx, const char* format, ...);
+JS_ReportErrorUTF8(JSContext* cx, const char* format, ...)
+    MOZ_FORMAT_PRINTF(2, 3);
 
 /*
  * Use an errorNumber to retrieve the format string, args are char*
@@ -5257,13 +5260,16 @@ JS_ReportErrorNumberUCArray(JSContext* cx, JSErrorCallback errorCallback,
  * being set, false otherwise.
  */
 extern JS_PUBLIC_API(bool)
-JS_ReportWarningASCII(JSContext* cx, const char* format, ...);
+JS_ReportWarningASCII(JSContext* cx, const char* format, ...)
+    MOZ_FORMAT_PRINTF(2, 3);
 
 extern JS_PUBLIC_API(bool)
-JS_ReportWarningLatin1(JSContext* cx, const char* format, ...);
+JS_ReportWarningLatin1(JSContext* cx, const char* format, ...)
+    MOZ_FORMAT_PRINTF(2, 3);
 
 extern JS_PUBLIC_API(bool)
-JS_ReportWarningUTF8(JSContext* cx, const char* format, ...);
+JS_ReportWarningUTF8(JSContext* cx, const char* format, ...)
+    MOZ_FORMAT_PRINTF(2, 3);
 
 extern JS_PUBLIC_API(bool)
 JS_ReportErrorFlagsAndNumberASCII(JSContext* cx, unsigned flags,
diff --git a/js/src/jsfriendapi.cpp b/js/src/jsfriendapi.cpp
index 061afb85aefa..83a83b3f637c 100644
--- a/js/src/jsfriendapi.cpp
+++ b/js/src/jsfriendapi.cpp
@@ -763,11 +763,16 @@ FormatValue(JSContext* cx, const Value& vArg, JSAutoByteString& bytes)
 
 // Wrapper for JS_sprintf_append() that reports allocation failure to the
 // context.
-template <typename... Args>
 static char*
-sprintf_append(JSContext* cx, char* buf, Args&&... args)
+MOZ_FORMAT_PRINTF(3, 4)
+sprintf_append(JSContext* cx, char* buf, const char* fmt, ...)
 {
-    char* result = JS_sprintf_append(buf, mozilla::Forward<Args>(args)...);
+    va_list ap;
+
+    va_start(ap, fmt);
+    char* result = JS_vsprintf_append(buf, fmt, ap);
+    va_end(ap);
+
     if (!result) {
         ReportOutOfMemory(cx);
         return nullptr;
diff --git a/js/src/jsobj.cpp b/js/src/jsobj.cpp
index 94be4fccd103..27321c2034c1 100644
--- a/js/src/jsobj.cpp
+++ b/js/src/jsobj.cpp
@@ -3630,11 +3630,11 @@ js::DumpBacktrace(JSContext* cx, FILE* fp)
             i.isWasm() ? 'W' :
             '?';
 
-        sprinter.printf("#%d %14p %c   %s:%d",
+        sprinter.printf("#%" PRIuSIZE " %14p %c   %s:%d",
                         depth, i.rawFramePtr(), frameType, filename, line);
 
         if (i.hasScript()) {
-            sprinter.printf(" (%p @ %d)\n",
+            sprinter.printf(" (%p @ %" PRIuSIZE ")\n",
                             i.script(), i.script()->pcToOffset(i.pc()));
         } else {
             sprinter.printf(" (%p)\n", i.pc());
diff --git a/js/src/jsopcode.cpp b/js/src/jsopcode.cpp
index a492b36831fa..ff340275806e 100644
--- a/js/src/jsopcode.cpp
+++ b/js/src/jsopcode.cpp
@@ -151,14 +151,14 @@ const char * PCCounts::numExecName = "interp";
 static MOZ_MUST_USE bool
 DumpIonScriptCounts(Sprinter* sp, HandleScript script, jit::IonScriptCounts* ionCounts)
 {
-    if (!sp->jsprintf("IonScript [%lu blocks]:\n", ionCounts->numBlocks()))
+    if (!sp->jsprintf("IonScript [%" PRIuSIZE " blocks]:\n", ionCounts->numBlocks()))
         return false;
 
     for (size_t i = 0; i < ionCounts->numBlocks(); i++) {
         const jit::IonBlockCounts& block = ionCounts->block(i);
         unsigned lineNumber = 0, columnNumber = 0;
         lineNumber = PCToLineNumber(script, script->offsetToPC(block.offset()), &columnNumber);
-        if (!sp->jsprintf("BB #%lu [%05u,%u,%u]",
+        if (!sp->jsprintf("BB #%" PRIu32 " [%05u,%u,%u]",
                           block.id(), block.offset(), lineNumber, columnNumber))
         {
             return false;
@@ -168,10 +168,10 @@ DumpIonScriptCounts(Sprinter* sp, HandleScript script, jit::IonScriptCounts* ion
                 return false;
         }
         for (size_t j = 0; j < block.numSuccessors(); j++) {
-            if (!sp->jsprintf(" -> #%lu", block.successor(j)))
+            if (!sp->jsprintf(" -> #%" PRIu32, block.successor(j)))
                 return false;
         }
-        if (!sp->jsprintf(" :: %llu hits\n", block.hitCount()))
+        if (!sp->jsprintf(" :: %" PRIu64 " hits\n", block.hitCount()))
             return false;
         if (!sp->jsprintf("%s\n", block.code()))
             return false;
diff --git a/js/src/jsprf.cpp b/js/src/jsprf.cpp
index 1f8c1a6dffc3..646b938de834 100644
--- a/js/src/jsprf.cpp
+++ b/js/src/jsprf.cpp
@@ -63,18 +63,18 @@ struct NumArgState
 typedef mozilla::Vector<NumArgState, 20, js::SystemAllocPolicy> NumArgStateVector;
 
 
-#define TYPE_INT16      0
-#define TYPE_UINT16     1
+#define TYPE_SHORT      0
+#define TYPE_USHORT     1
 #define TYPE_INTN       2
 #define TYPE_UINTN      3
-#define TYPE_INT32      4
-#define TYPE_UINT32     5
-#define TYPE_INT64      6
-#define TYPE_UINT64     7
+#define TYPE_LONG       4
+#define TYPE_ULONG      5
+#define TYPE_LONGLONG   6
+#define TYPE_ULONGLONG  7
 #define TYPE_STRING     8
 #define TYPE_DOUBLE     9
 #define TYPE_INTSTR     10
-#define TYPE_WSTRING    11
+#define TYPE_POINTER    11
 #define TYPE_UNKNOWN    20
 
 #define FLAG_LEFT       0x1
@@ -89,31 +89,9 @@ generic_write(SprintfState* ss, const char* src, size_t srclen)
     return (*ss->stuff)(ss, src, srclen);
 }
 
-inline bool
-generic_write(SprintfState* ss, const char16_t* src, size_t srclen)
-{
-    const size_t CHUNK_SIZE = 64;
-    char chunk[CHUNK_SIZE];
-
-    size_t j = 0;
-    size_t i = 0;
-    while (i < srclen) {
-        // FIXME: truncates characters to 8 bits
-        chunk[j++] = char(src[i++]);
-
-        if (j == CHUNK_SIZE || i == srclen) {
-            if (!(*ss->stuff)(ss, chunk, j))
-                return false;
-            j = 0;
-        }
-    }
-    return true;
-}
-
 // Fill into the buffer using the data in src
-template <typename Char>
 static bool
-fill2(SprintfState* ss, const Char* src, int srclen, int width, int flags)
+fill2(SprintfState* ss, const char* src, int srclen, int width, int flags)
 {
     char space = ' ';
 
@@ -318,19 +296,16 @@ static bool cvt_f(SprintfState* ss, double d, const char* fmt0, const char* fmt1
 }
 
 static inline const char* generic_null_str(const char*) { return "(null)"; }
-static inline const char16_t* generic_null_str(const char16_t*) { return u"(null)"; }
 
 static inline size_t generic_strlen(const char* s) { return strlen(s); }
-static inline size_t generic_strlen(const char16_t* s) { return js_strlen(s); }
 
 /*
  * Convert a string into its printable form.  "width" is the output
  * width. "prec" is the maximum number of characters of "s" to output,
  * where -1 means until NUL.
  */
-template <typename Char>
 static bool
-cvt_s(SprintfState* ss, const Char* s, int width, int prec, int flags)
+cvt_s(SprintfState* ss, const char* s, int width, int prec, int flags)
 {
     if (prec == 0)
         return true;
@@ -452,23 +427,24 @@ BuildArgArray(const char* fmt, va_list ap, NumArgStateVector& nas)
         // size
         nas[cn].type = TYPE_INTN;
         if (c == 'h') {
-            nas[cn].type = TYPE_INT16;
+            nas[cn].type = TYPE_SHORT;
             c = *p++;
         } else if (c == 'L') {
-            // XXX not quite sure here
-            nas[cn].type = TYPE_INT64;
+            nas[cn].type = TYPE_LONGLONG;
             c = *p++;
         } else if (c == 'l') {
-            nas[cn].type = TYPE_INT32;
+            nas[cn].type = TYPE_LONG;
             c = *p++;
             if (c == 'l') {
-                nas[cn].type = TYPE_INT64;
+                nas[cn].type = TYPE_LONGLONG;
                 c = *p++;
             }
         } else if (c == 'z' || c == 'I') {
-            static_assert(sizeof(size_t) == sizeof(int32_t) || sizeof(size_t) == sizeof(int64_t),
+            static_assert(sizeof(size_t) == sizeof(int) || sizeof(size_t) == sizeof(long) ||
+                          sizeof(size_t) == sizeof(long long),
                           "size_t is not one of the expected sizes");
-            nas[cn].type = sizeof(size_t) == sizeof(int64_t) ? TYPE_INT64 : TYPE_INT32;
+            nas[cn].type = sizeof(size_t) == sizeof(int) ? TYPE_INTN :
+                sizeof(size_t) == sizeof(long) ? TYPE_LONG : TYPE_LONGLONG;
             c = *p++;
         }
 
@@ -490,16 +466,7 @@ BuildArgArray(const char* fmt, va_list ap, NumArgStateVector& nas)
             break;
 
         case 'p':
-            // XXX should use cpp
-            if (sizeof(void*) == sizeof(int32_t)) {
-                nas[cn].type = TYPE_UINT32;
-            } else if (sizeof(void*) == sizeof(int64_t)) {
-                nas[cn].type = TYPE_UINT64;
-            } else if (sizeof(void*) == sizeof(int)) {
-                nas[cn].type = TYPE_UINTN;
-            } else {
-                nas[cn].type = TYPE_UNKNOWN;
-            }
+            nas[cn].type = TYPE_POINTER;
             break;
 
         case 'C':
@@ -512,7 +479,7 @@ BuildArgArray(const char* fmt, va_list ap, NumArgStateVector& nas)
             break;
 
         case 's':
-            nas[cn].type = (nas[cn].type == TYPE_UINT16) ? TYPE_WSTRING : TYPE_STRING;
+            nas[cn].type = TYPE_STRING;
             break;
 
         case 'n':
@@ -544,18 +511,18 @@ BuildArgArray(const char* fmt, va_list ap, NumArgStateVector& nas)
         VARARGS_ASSIGN(nas[cn].ap, ap);
 
         switch (nas[cn].type) {
-        case TYPE_INT16:
-        case TYPE_UINT16:
+        case TYPE_SHORT:
+        case TYPE_USHORT:
         case TYPE_INTN:
         case TYPE_UINTN:        (void) va_arg(ap, int);         break;
-        case TYPE_INT32:        (void) va_arg(ap, int32_t);     break;
-        case TYPE_UINT32:       (void) va_arg(ap, uint32_t);    break;
-        case TYPE_INT64:        (void) va_arg(ap, int64_t);     break;
-        case TYPE_UINT64:       (void) va_arg(ap, uint64_t);    break;
+        case TYPE_LONG:         (void) va_arg(ap, long);        break;
+        case TYPE_ULONG:        (void) va_arg(ap, unsigned long); break;
+        case TYPE_LONGLONG:     (void) va_arg(ap, long long);   break;
+        case TYPE_ULONGLONG:    (void) va_arg(ap, unsigned long long); break;
         case TYPE_STRING:       (void) va_arg(ap, char*);       break;
-        case TYPE_WSTRING:      (void) va_arg(ap, char16_t*);   break;
         case TYPE_INTSTR:       (void) va_arg(ap, int*);        break;
         case TYPE_DOUBLE:       (void) va_arg(ap, double);      break;
+        case TYPE_POINTER:      (void) va_arg(ap, void*);       break;
 
         default: MOZ_CRASH();
         }
@@ -576,14 +543,13 @@ dosprintf(SprintfState* ss, const char* fmt, va_list ap)
     int flags, width, prec, radix, type;
     union {
         char ch;
-        char16_t wch;
         int i;
         long l;
-        int64_t ll;
+        long long ll;
         double d;
         const char* s;
-        const char16_t* ws;
         int* ip;
+        void* p;
     } u;
     const char* fmt0;
     static const char hex[] = "0123456789abcdef";
@@ -685,23 +651,24 @@ dosprintf(SprintfState* ss, const char* fmt, va_list ap)
         // size
         type = TYPE_INTN;
         if (c == 'h') {
-            type = TYPE_INT16;
+            type = TYPE_SHORT;
             c = *fmt++;
         } else if (c == 'L') {
-            // XXX not quite sure here
-            type = TYPE_INT64;
+            type = TYPE_LONGLONG;
             c = *fmt++;
         } else if (c == 'l') {
-            type = TYPE_INT32;
+            type = TYPE_LONG;
             c = *fmt++;
             if (c == 'l') {
-                type = TYPE_INT64;
+                type = TYPE_LONGLONG;
                 c = *fmt++;
             }
         } else if (c == 'z' || c == 'I') {
-            static_assert(sizeof(size_t) == sizeof(int32_t) || sizeof(size_t) == sizeof(int64_t),
+            static_assert(sizeof(size_t) == sizeof(int) || sizeof(size_t) == sizeof(long) ||
+                          sizeof(size_t) == sizeof(long long),
                           "size_t is not one of the expected sizes");
-            type = sizeof(size_t) == sizeof(int64_t) ? TYPE_INT64 : TYPE_INT32;
+            type = sizeof(size_t) == sizeof(int) ? TYPE_INTN :
+                sizeof(size_t) == sizeof(long) ? TYPE_LONG : TYPE_LONGLONG;
             c = *fmt++;
         }
 
@@ -735,15 +702,15 @@ dosprintf(SprintfState* ss, const char* fmt, va_list ap)
 
           fetch_and_convert:
             switch (type) {
-              case TYPE_INT16:
+              case TYPE_SHORT:
                 u.l = va_arg(ap, int);
                 if (u.l < 0) {
                     u.l = -u.l;
                     flags |= FLAG_NEG;
                 }
                 goto do_long;
-              case TYPE_UINT16:
-                u.l = va_arg(ap, int) & 0xffff;
+              case TYPE_USHORT:
+                u.l = (unsigned short) va_arg(ap, unsigned int);
                 goto do_long;
               case TYPE_INTN:
                 u.l = va_arg(ap, int);
@@ -756,30 +723,33 @@ dosprintf(SprintfState* ss, const char* fmt, va_list ap)
                 u.l = (long)va_arg(ap, unsigned int);
                 goto do_long;
 
-              case TYPE_INT32:
-                u.l = va_arg(ap, int32_t);
+              case TYPE_LONG:
+                u.l = va_arg(ap, long);
                 if (u.l < 0) {
                     u.l = -u.l;
                     flags |= FLAG_NEG;
                 }
                 goto do_long;
-              case TYPE_UINT32:
-                u.l = (long)va_arg(ap, uint32_t);
+              case TYPE_ULONG:
+                u.l = (long)va_arg(ap, unsigned long);
               do_long:
                 if (!cvt_l(ss, u.l, width, prec, radix, type, flags, hexp))
                     return false;
 
                 break;
 
-              case TYPE_INT64:
-                u.ll = va_arg(ap, int64_t);
+              case TYPE_LONGLONG:
+                u.ll = va_arg(ap, long long);
                 if (u.ll < 0) {
                     u.ll = -u.ll;
                     flags |= FLAG_NEG;
                 }
                 goto do_longlong;
-              case TYPE_UINT64:
-                u.ll = va_arg(ap, uint64_t);
+              case TYPE_POINTER:
+                u.ll = (uintptr_t)va_arg(ap, void*);
+                goto do_longlong;
+              case TYPE_ULONGLONG:
+                u.ll = va_arg(ap, unsigned long long);
               do_longlong:
                 if (!cvt_ll(ss, u.ll, width, prec, radix, type, flags, hexp))
                     return false;
@@ -816,7 +786,7 @@ dosprintf(SprintfState* ss, const char* fmt, va_list ap)
                 }
             }
             switch (type) {
-              case TYPE_INT16:
+              case TYPE_SHORT:
               case TYPE_INTN:
                 u.ch = va_arg(ap, int);
                 if (!(*ss->stuff)(ss, &u.ch, 1))
@@ -832,16 +802,7 @@ dosprintf(SprintfState* ss, const char* fmt, va_list ap)
             break;
 
           case 'p':
-            if (sizeof(void*) == sizeof(int32_t)) {
-                type = TYPE_UINT32;
-            } else if (sizeof(void*) == sizeof(int64_t)) {
-                type = TYPE_UINT64;
-            } else if (sizeof(void*) == sizeof(int)) {
-                type = TYPE_UINTN;
-            } else {
-                MOZ_ASSERT(0);
-                break;
-            }
+            type = TYPE_POINTER;
             radix = 16;
             goto fetch_and_convert;
 
@@ -856,15 +817,9 @@ dosprintf(SprintfState* ss, const char* fmt, va_list ap)
 #endif
 
           case 's':
-            if(type == TYPE_INT16) {
-                u.ws = va_arg(ap, const char16_t*);
-                if (!cvt_s(ss, u.ws, width, prec, flags))
-                    return false;
-            } else {
-                u.s = va_arg(ap, const char*);
-                if (!cvt_s(ss, u.s, width, prec, flags))
-                    return false;
-            }
+            u.s = va_arg(ap, const char*);
+            if (!cvt_s(ss, u.s, width, prec, flags))
+                return false;
             break;
 
           case 'n':
@@ -1004,18 +959,18 @@ JS_vsprintf_append(char* last, const char* fmt, va_list ap)
     return ss.base;
 }
 
-#undef TYPE_INT16
-#undef TYPE_UINT16
+#undef TYPE_SHORT
+#undef TYPE_USHORT
 #undef TYPE_INTN
 #undef TYPE_UINTN
-#undef TYPE_INT32
-#undef TYPE_UINT32
-#undef TYPE_INT64
-#undef TYPE_UINT64
+#undef TYPE_LONG
+#undef TYPE_ULONG
+#undef TYPE_LONGLONG
+#undef TYPE_ULONGLONG
 #undef TYPE_STRING
 #undef TYPE_DOUBLE
 #undef TYPE_INTSTR
-#undef TYPE_WSTRING
+#undef TYPE_POINTER
 #undef TYPE_UNKNOWN
 
 #undef FLAG_LEFT
diff --git a/js/src/jsprf.h b/js/src/jsprf.h
index 3bdbe638472c..b84b5a5c9864 100644
--- a/js/src/jsprf.h
+++ b/js/src/jsprf.h
@@ -14,11 +14,13 @@
 **      %x - unsigned hex
 **      %X - unsigned uppercase hex
 **      %o - unsigned octal
-**      %hd, %hu, %hx, %hX, %ho - 16-bit versions of above
-**      %ld, %lu, %lx, %lX, %lo - 32-bit versions of above
-**      %lld, %llu, %llx, %llX, %llo - 64 bit versions of above
-**      %s - ascii string
-**      %hs - ucs2 string
+**      %hd, %hu, %hx, %hX, %ho - "short" versions of above
+**      %ld, %lu, %lx, %lX, %lo - "long" versions of above
+**      %lld, %llu, %llx, %llX, %llo - "long long" versions of above
+**      %zd, %zo, %zu, %zx, %zX - size_t versions of above
+**      %Id, %Io, %Iu, %Ix, %IX - size_t versions of above (for Windows compat)
+**           You should use PRI*SIZE macros instead
+**      %s - string
 **      %c - character
 **      %p - pointer (deals with machine dependent pointer size)
 **      %f - float
@@ -37,7 +39,8 @@
 ** buffer on success, nullptr on failure. Call "JS_smprintf_free" to release
 ** the memory returned.
 */
-extern JS_PUBLIC_API(char*) JS_smprintf(const char* fmt, ...);
+extern JS_PUBLIC_API(char*) JS_smprintf(const char* fmt, ...)
+    MOZ_FORMAT_PRINTF(1, 2);
 
 /*
 ** Free the memory allocated, for the caller, by JS_smprintf
@@ -51,7 +54,8 @@ extern JS_PUBLIC_API(void) JS_smprintf_free(char* mem);
 ** will allocate the initial string. The return value is the new value of
 ** last for subsequent calls, or nullptr if there is a malloc failure.
 */
-extern JS_PUBLIC_API(char*) JS_sprintf_append(char* last, const char* fmt, ...);
+extern JS_PUBLIC_API(char*) JS_sprintf_append(char* last, const char* fmt, ...)
+    MOZ_FORMAT_PRINTF(2, 3);
 
 /*
 ** va_list forms of the above.
diff --git a/js/src/moz.build b/js/src/moz.build
index bf2081f7a7b5..546a396753a7 100644
--- a/js/src/moz.build
+++ b/js/src/moz.build
@@ -784,7 +784,7 @@ if CONFIG['JS_HAS_CTYPES']:
         DEFINES['FFI_BUILDING'] = True
 
 if CONFIG['GNU_CXX']:
-    CXXFLAGS += ['-Wno-shadow']
+    CXXFLAGS += ['-Wno-shadow', '-Werror=format']
 
 # Suppress warnings in third-party code.
 if CONFIG['CLANG_CXX']:
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
index 4ffda095c894..67da80bcf8dd 100644
--- a/js/src/shell/js.cpp
+++ b/js/src/shell/js.cpp
@@ -5247,7 +5247,7 @@ ReflectTrackedOptimizations(JSContext* cx, unsigned argc, Value* vp)
             uint8_t* addr = ion->method()->raw() + endOffset;
             entry.youngestFrameLocationAtAddr(rt, addr, &script, &pc);
 
-            if (!sp.jsprintf("{\"location\":\"%s:%u\",\"offset\":%u,\"index\":%u}%s",
+            if (!sp.jsprintf("{\"location\":\"%s:%" PRIuSIZE "\",\"offset\":%" PRIuSIZE ",\"index\":%u}%s",
                              script->filename(), script->lineno(), script->pcToOffset(pc), index,
                              iter.more() ? "," : ""))
             {
diff --git a/js/src/shell/jsoptparse.cpp b/js/src/shell/jsoptparse.cpp
index 5e1a3aa09fdc..eaf4042d3bf4 100644
--- a/js/src/shell/jsoptparse.cpp
+++ b/js/src/shell/jsoptparse.cpp
@@ -264,7 +264,7 @@ OptionParser::extractValue(size_t argc, char** argv, size_t* i, char** value)
     if (eq) {
         *value = eq + 1;
         if (*value[0] == '\0')
-            return error("A value is required for option %.*s", eq - argv[*i], argv[*i]);
+            return error("A value is required for option %.*s", (int) (eq - argv[*i]), argv[*i]);
         return Okay;
     }
 
diff --git a/js/src/shell/jsoptparse.h b/js/src/shell/jsoptparse.h
index b2a24348186a..274978130ea3 100644
--- a/js/src/shell/jsoptparse.h
+++ b/js/src/shell/jsoptparse.h
@@ -228,7 +228,7 @@ class OptionParser
     Option* findArgument(const char* name);
     const Option* findArgument(const char* name) const;
 
-    Result error(const char* fmt, ...);
+    Result error(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
     Result extractValue(size_t argc, char** argv, size_t* i, char** value);
     Result handleArg(size_t argc, char** argv, size_t* i, bool* optsAllowed);
     Result handleOption(Option* opt, size_t argc, char** argv, size_t* i, bool* optsAllowed);
diff --git a/js/src/shell/moz.build b/js/src/shell/moz.build
index 77475b241fa8..72ea8145cc31 100644
--- a/js/src/shell/moz.build
+++ b/js/src/shell/moz.build
@@ -51,7 +51,7 @@ shellmoduleloader.inputs = [
 ]
 
 if CONFIG['GNU_CXX']:
-    CXXFLAGS += ['-Wno-shadow']
+    CXXFLAGS += ['-Wno-shadow', '-Werror=format']
 
 # This is intended as a temporary workaround to enable VS2015.
 if CONFIG['_MSC_VER']:
diff --git a/js/src/vm/CodeCoverage.cpp b/js/src/vm/CodeCoverage.cpp
index 280256b66eef..e7146a32a3be 100644
--- a/js/src/vm/CodeCoverage.cpp
+++ b/js/src/vm/CodeCoverage.cpp
@@ -91,16 +91,16 @@ LCovSource::exportInto(GenericPrinter& out) const
 
     outFN_.exportInto(out);
     outFNDA_.exportInto(out);
-    out.printf("FNF:%d\n", numFunctionsFound_);
-    out.printf("FNH:%d\n", numFunctionsHit_);
+    out.printf("FNF:%" PRIuSIZE "\n", numFunctionsFound_);
+    out.printf("FNH:%" PRIuSIZE "\n", numFunctionsHit_);
 
     outBRDA_.exportInto(out);
-    out.printf("BRF:%d\n", numBranchesFound_);
-    out.printf("BRH:%d\n", numBranchesHit_);
+    out.printf("BRF:%" PRIuSIZE "\n", numBranchesFound_);
+    out.printf("BRH:%" PRIuSIZE "\n", numBranchesHit_);
 
     outDA_.exportInto(out);
-    out.printf("LF:%d\n", numLinesInstrumented_);
-    out.printf("LH:%d\n", numLinesHit_);
+    out.printf("LF:%" PRIuSIZE "\n", numLinesInstrumented_);
+    out.printf("LH:%" PRIuSIZE "\n", numLinesHit_);
 
     out.put("end_of_record\n");
 }
@@ -130,7 +130,7 @@ bool
 LCovSource::writeScript(JSScript* script)
 {
     numFunctionsFound_++;
-    outFN_.printf("FN:%d,", script->lineno());
+    outFN_.printf("FN:%" PRIuSIZE ",", script->lineno());
     if (!writeScriptName(outFN_, script))
         return false;
     outFN_.put("\n", 1);
@@ -191,7 +191,7 @@ LCovSource::writeScript(JSScript* script)
             }
 
             if (oldLine != lineno && fallsthrough) {
-                outDA_.printf("DA:%d,%" PRIu64 "\n", lineno, hits);
+                outDA_.printf("DA:%" PRIuSIZE ",%" PRIu64 "\n", lineno, hits);
 
                 // Count the number of lines instrumented & hit.
                 numLinesInstrumented_++;
@@ -220,13 +220,13 @@ LCovSource::writeScript(JSScript* script)
             }
 
             uint64_t taken = hits - fallthroughHits;
-            outBRDA_.printf("BRDA:%d,%d,0,", lineno, branchId);
+            outBRDA_.printf("BRDA:%" PRIuSIZE ",%" PRIuSIZE ",0,", lineno, branchId);
             if (taken)
                 outBRDA_.printf("%" PRIu64 "\n", taken);
             else
                 outBRDA_.put("-\n", 2);
 
-            outBRDA_.printf("BRDA:%d,%d,1,", lineno, branchId);
+            outBRDA_.printf("BRDA:%" PRIuSIZE ",%" PRIuSIZE ",1,", lineno, branchId);
             if (fallthroughHits)
                 outBRDA_.printf("%" PRIu64 "\n", fallthroughHits);
             else
@@ -308,7 +308,8 @@ LCovSource::writeScript(JSScript* script)
                         caseHits -= fallsThroughHits;
                     }
 
-                    outBRDA_.printf("BRDA:%d,%d,%d,", lineno, branchId, caseId);
+                    outBRDA_.printf("BRDA:%" PRIuSIZE ",%" PRIuSIZE ",%" PRIuSIZE ",",
+                                    lineno, branchId, caseId);
                     if (caseHits)
                         outBRDA_.printf("%" PRIu64 "\n", caseHits);
                     else
@@ -359,7 +360,8 @@ LCovSource::writeScript(JSScript* script)
             }
 
             if (defaultHasOwnClause) {
-                outBRDA_.printf("BRDA:%d,%d,%d,", lineno, branchId, caseId);
+                outBRDA_.printf("BRDA:%" PRIuSIZE ",%" PRIuSIZE ",%" PRIuSIZE ",",
+                                lineno, branchId, caseId);
                 if (defaultHits)
                     outBRDA_.printf("%" PRIu64 "\n", defaultHits);
                 else
diff --git a/js/src/vm/Printer.h b/js/src/vm/Printer.h
index ae70d59fa114..3ee76da44d5e 100644
--- a/js/src/vm/Printer.h
+++ b/js/src/vm/Printer.h
@@ -43,7 +43,7 @@ class GenericPrinter
     }
 
     // Prints a formatted string into the buffer.
-    virtual int printf(const char* fmt, ...);
+    virtual int printf(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
     virtual int vprintf(const char* fmt, va_list ap);
 
     // Report that a string operation failed to get the memory it requested. The
@@ -115,7 +115,7 @@ class Sprinter final : public GenericPrinter
     // Format the given format/arguments as if by JS_vsmprintf, then put it.
     // Return true on success, else return false and report an error (typically
     // OOM).
-    MOZ_MUST_USE bool jsprintf(const char* fmt, ...);
+    MOZ_MUST_USE bool jsprintf(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
 
     // Prints a formatted string into the buffer.
     virtual int vprintf(const char* fmt, va_list ap) override;
@@ -157,7 +157,7 @@ class Fprinter final : public GenericPrinter
     using GenericPrinter::put; // pick up |inline int put(const char* s);|
 
     // Prints a formatted string into the buffer.
-    virtual int printf(const char* fmt, ...) override;
+    virtual int printf(const char* fmt, ...) override MOZ_FORMAT_PRINTF(2, 3);
     virtual int vprintf(const char* fmt, va_list ap) override;
 };
 
@@ -203,7 +203,7 @@ class LSprinter final : public GenericPrinter
     using GenericPrinter::put; // pick up |inline int put(const char* s);|
 
     // Prints a formatted string into the buffer.
-    virtual int printf(const char* fmt, ...) override;
+    virtual int printf(const char* fmt, ...) override MOZ_FORMAT_PRINTF(2, 3);
     virtual int vprintf(const char* fmt, va_list ap) override;
 
     // Report that a string operation failed to get the memory it requested. The
diff --git a/js/src/vm/String.cpp b/js/src/vm/String.cpp
index 1d38c48239da..eed04d3fab4f 100644
--- a/js/src/vm/String.cpp
+++ b/js/src/vm/String.cpp
@@ -10,6 +10,7 @@
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/PodOperations.h"
 #include "mozilla/RangedPtr.h"
+#include "mozilla/SizePrintfMacros.h"
 #include "mozilla/TypeTraits.h"
 #include "mozilla/Unused.h"
 
@@ -187,7 +188,7 @@ JSString::dumpRepresentationHeader(FILE* fp, int indent, const char* subclass) c
     uint32_t flags = d.u1.flags;
     // Print the string's address as an actual C++ expression, to facilitate
     // copy-and-paste into a debugger.
-    fprintf(fp, "((%s*) %p) length: %zu  flags: 0x%x", subclass, this, length(), flags);
+    fprintf(fp, "((%s*) %p) length: %" PRIuSIZE "  flags: 0x%x", subclass, this, length(), flags);
     if (flags & FLAT_BIT)               fputs(" FLAT", fp);
     if (flags & HAS_BASE_BIT)           fputs(" HAS_BASE", fp);
     if (flags & INLINE_CHARS_BIT)       fputs(" INLINE_CHARS", fp);
@@ -703,7 +704,7 @@ JSDependentString::dumpRepresentation(FILE* fp, int indent) const
     dumpRepresentationHeader(fp, indent, "JSDependentString");
     indent += 2;
 
-    fprintf(fp, "%*soffset: %zu\n", indent, "", baseOffset());
+    fprintf(fp, "%*soffset: %" PRIuSIZE "\n", indent, "", baseOffset());
     fprintf(fp, "%*sbase: ", indent, "");
     base()->dumpRepresentation(fp, indent);
 }
@@ -1363,7 +1364,7 @@ JSExtensibleString::dumpRepresentation(FILE* fp, int indent) const
     dumpRepresentationHeader(fp, indent, "JSExtensibleString");
     indent += 2;
 
-    fprintf(fp, "%*scapacity: %zu\n", indent, "", capacity());
+    fprintf(fp, "%*scapacity: %" PRIuSIZE "\n", indent, "", capacity());
     dumpRepresentationChars(fp, indent);
 }
 
diff --git a/js/src/vm/TraceLoggingGraph.cpp b/js/src/vm/TraceLoggingGraph.cpp
index 16d270b7e54a..6f6792e98040 100644
--- a/js/src/vm/TraceLoggingGraph.cpp
+++ b/js/src/vm/TraceLoggingGraph.cpp
@@ -50,6 +50,7 @@ TraceLoggerGraphState* traceLoggerGraphState = nullptr;
 // are allowed, with %u standing for a full 32-bit number and %d standing for
 // an up to 3-digit number.
 static js::UniqueChars
+MOZ_FORMAT_PRINTF(1, 2)
 AllocTraceLogFilename(const char* pattern, ...) {
     js::UniqueChars filename;
 
diff --git a/js/src/vm/TypeInference.cpp b/js/src/vm/TypeInference.cpp
index 97a92fccee95..762edf71d3a5 100644
--- a/js/src/vm/TypeInference.cpp
+++ b/js/src/vm/TypeInference.cpp
@@ -237,6 +237,7 @@ js::InferSpewImpl(const char* fmt, ...)
 #endif
 
 MOZ_NORETURN MOZ_COLD static void
+MOZ_FORMAT_PRINTF(2, 3)
 TypeFailure(JSContext* cx, const char* fmt, ...)
 {
     char msgbuf[1024]; /* Larger error messages will be truncated */
@@ -3288,7 +3289,7 @@ js::TypeMonitorResult(JSContext* cx, JSScript* script, jsbytecode* pc, TypeSet::
     if (types->hasType(type))
         return;
 
-    InferSpew(ISpewOps, "bytecodeType: %p %05u: %s",
+    InferSpew(ISpewOps, "bytecodeType: %p %05" PRIuSIZE ": %s",
               script, script->pcToOffset(pc), TypeSet::TypeString(type));
     types->addType(cx, type);
 }
diff --git a/js/src/vm/TypeInference.h b/js/src/vm/TypeInference.h
index ee243bf299f0..26522727c98f 100644
--- a/js/src/vm/TypeInference.h
+++ b/js/src/vm/TypeInference.h
@@ -1296,7 +1296,7 @@ const char * InferSpewColor(TypeConstraint* constraint);
 const char * InferSpewColor(TypeSet* types);
 
 #define InferSpew(channel, ...) if (InferSpewActive(channel)) { InferSpewImpl(__VA_ARGS__); } else {}
-void InferSpewImpl(const char* fmt, ...);
+void InferSpewImpl(const char* fmt, ...) MOZ_FORMAT_PRINTF(1, 2);
 
 /* Check that the type property for id in group contains value. */
 bool ObjectGroupHasProperty(JSContext* cx, ObjectGroup* group, jsid id, const Value& value);
diff --git a/js/xpconnect/loader/mozJSComponentLoader.cpp b/js/xpconnect/loader/mozJSComponentLoader.cpp
index 2f0c0ff40a56..95c214867758 100644
--- a/js/xpconnect/loader/mozJSComponentLoader.cpp
+++ b/js/xpconnect/loader/mozJSComponentLoader.cpp
@@ -154,6 +154,7 @@ private:
 };
 
 static nsresult
+MOZ_FORMAT_PRINTF(2, 3)
 ReportOnCallerUTF8(JSContext* callerContext,
                    const char* format, ...) {
     if (!callerContext) {
@@ -177,6 +178,7 @@ ReportOnCallerUTF8(JSContext* callerContext,
 }
 
 static nsresult
+MOZ_FORMAT_PRINTF(2, 3)
 ReportOnCallerUTF8(JSCLContextHelper& helper,
                    const char* format, ...)
 {
diff --git a/js/xpconnect/src/XPCThrower.cpp b/js/xpconnect/src/XPCThrower.cpp
index ad479b4e3eb8..4a37e1554287 100644
--- a/js/xpconnect/src/XPCThrower.cpp
+++ b/js/xpconnect/src/XPCThrower.cpp
@@ -116,9 +116,9 @@ XPCThrower::ThrowBadResult(nsresult rv, nsresult result, XPCCallContext& ccx)
         format = "";
 
     if (nsXPCException::NameAndFormatForNSResult(result, &name, nullptr) && name)
-        sz = JS_smprintf("%s 0x%x (%s)", format, result, name);
+        sz = JS_smprintf("%s 0x%x (%s)", format, (unsigned) result, name);
     else
-        sz = JS_smprintf("%s 0x%x", format, result);
+        sz = JS_smprintf("%s 0x%x", format, (unsigned) result);
     NS_ENSURE_TRUE_VOID(sz);
 
     if (sz && sVerbose)
diff --git a/js/xpconnect/src/XPCWrappedJSClass.cpp b/js/xpconnect/src/XPCWrappedJSClass.cpp
index 518c8c94ce62..0cf82633c6c9 100644
--- a/js/xpconnect/src/XPCWrappedJSClass.cpp
+++ b/js/xpconnect/src/XPCWrappedJSClass.cpp
@@ -971,7 +971,7 @@ nsXPCWrappedJSClass::CallMethod(nsXPCWrappedJS* wrapper, uint16_t methodIndex,
         const char* str = "IDL methods marked with [implicit_jscontext] "
                           "or [optional_argc] may not be implemented in JS";
         // Throw and warn for good measure.
-        JS_ReportErrorASCII(cx, str);
+        JS_ReportErrorASCII(cx, "%s", str);
         NS_WARNING(str);
         return CheckForException(ccx, aes, name, GetInterfaceName());
     }
diff --git a/js/xpconnect/src/moz.build b/js/xpconnect/src/moz.build
index 9108fd66aca2..94d58577cc79 100644
--- a/js/xpconnect/src/moz.build
+++ b/js/xpconnect/src/moz.build
@@ -72,4 +72,4 @@ if CONFIG['MOZ_B2G_BT']:
     ]
 
 if CONFIG['GNU_CXX']:
-    CXXFLAGS += ['-Wno-shadow']
+    CXXFLAGS += ['-Wno-shadow', '-Werror=format']
diff --git a/js/xpconnect/wrappers/AccessCheck.cpp b/js/xpconnect/wrappers/AccessCheck.cpp
index 66e96d04c34a..9f468931f197 100644
--- a/js/xpconnect/wrappers/AccessCheck.cpp
+++ b/js/xpconnect/wrappers/AccessCheck.cpp
@@ -274,7 +274,7 @@ static void
 EnterAndThrowASCII(JSContext* cx, JSObject* wrapper, const char* msg)
 {
     JSAutoCompartment ac(cx, wrapper);
-    JS_ReportErrorASCII(cx, msg);
+    JS_ReportErrorASCII(cx, "%s", msg);
 }
 
 bool
diff --git a/layout/base/nsCSSFrameConstructor.cpp b/layout/base/nsCSSFrameConstructor.cpp
index 487c5a2bf167..8c7e66c9aa1d 100644
--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -12805,11 +12805,7 @@ Iterator::AppendItemsToList(const Iterator& aEnd,
   }
 
   // Move our entire list of items into the empty target list.
-  // XXX: If LinkedList supports move assignment, we could use
-  // aTargetList.mItems = Move(mList.mItems);
-  aTargetList.mItems.~LinkedList<FrameConstructionItem>();
-  new (&aTargetList.mItems) LinkedList<FrameConstructionItem>(
-    Move(mList.mItems));
+  aTargetList.mItems = Move(mList.mItems);
 
   // Copy over the various counters
   aTargetList.mInlineCount = mList.mInlineCount;
diff --git a/layout/generic/nsBlockFrame.cpp b/layout/generic/nsBlockFrame.cpp
index a5431e2ce3a7..1178d2180315 100644
--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -1410,12 +1410,11 @@ nsBlockFrame::Reflow(nsPresContext*           aPresContext,
       // calculating hypothetical position of absolutely-positioned
       // frames. The line cursor is immediately cleared afterward to
       // avoid affecting the display list generation.
-      SetupLineCursor();
+      AutoLineCursorSetup autoLineCursor(this);
       absoluteContainer->Reflow(this, aPresContext, *reflowInput,
                                 state.mReflowStatus,
                                 containingBlock, flags,
                                 &aMetrics.mOverflowAreas);
-      ClearLineCursor();
     }
   }
 
diff --git a/layout/generic/nsBlockFrame.h b/layout/generic/nsBlockFrame.h
index ec009fcf134f..8db16e8bb568 100644
--- a/layout/generic/nsBlockFrame.h
+++ b/layout/generic/nsBlockFrame.h
@@ -153,8 +153,12 @@ public:
   virtual mozilla::a11y::AccType AccessibleType() override;
 #endif
 
-  // line cursor methods to speed up searching for the line(s)
-  // containing a point. The basic idea is that we set the cursor
+  // Line cursor methods to speed up line searching in which one query
+  // result is expected to be close to the next in general. This is
+  // mainly for searching line(s) containing a point. It is also used
+  // as a cache for local computation. Use AutoLineCursorSetup for the
+  // latter case so that it wouldn't interact unexpectedly with the
+  // former. The basic idea for the former is that we set the cursor
   // property if the lines' overflowArea.VisualOverflow().ys and
   // overflowArea.VisualOverflow().yMosts are non-decreasing
   // (considering only non-empty overflowArea.VisualOverflow()s; empty
@@ -179,6 +183,36 @@ public:
   // building the display list of this frame.
   void SetupLineCursor();
 
+  /**
+   * Helper RAII class for automatically set and clear line cursor for
+   * temporary use. If the frame already has line cursor, this would be
+   * a no-op.
+   */
+  class MOZ_STACK_CLASS AutoLineCursorSetup
+  {
+  public:
+    explicit AutoLineCursorSetup(nsBlockFrame* aFrame)
+      : mFrame(aFrame)
+      , mOrigCursor(aFrame->GetLineCursor())
+    {
+      if (!mOrigCursor) {
+        mFrame->SetupLineCursor();
+      }
+    }
+    ~AutoLineCursorSetup()
+    {
+      if (mOrigCursor) {
+        mFrame->Properties().Set(LineCursorProperty(), mOrigCursor);
+      } else {
+        mFrame->ClearLineCursor();
+      }
+    }
+
+  private:
+    nsBlockFrame* mFrame;
+    nsLineBox* mOrigCursor;
+  };
+
   virtual void ChildIsDirty(nsIFrame* aChild) override;
   virtual bool IsVisibleInSelection(nsISelection* aSelection) override;
 
@@ -368,9 +402,9 @@ protected:
 #endif
 
   NS_DECLARE_FRAME_PROPERTY_WITHOUT_DTOR(LineCursorProperty, nsLineBox)
+  bool HasLineCursor() { return GetStateBits() & NS_BLOCK_HAS_LINE_CURSOR; }
   nsLineBox* GetLineCursor() {
-    return (GetStateBits() & NS_BLOCK_HAS_LINE_CURSOR) ?
-      Properties().Get(LineCursorProperty()) : nullptr;
+    return HasLineCursor() ? Properties().Get(LineCursorProperty()) : nullptr;
   }
 
   nsLineBox* NewLineBox(nsIFrame* aFrame, bool aIsBlock) {
diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index 8d0b11b65dcd..8bba88c0304e 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -9634,17 +9634,10 @@ static void TransformChars(nsTextFrame* aFrame, const nsStyleText* aStyle,
 }
 
 static bool
-LineEndsInHardLineBreak(nsTextFrame* aFrame)
+LineEndsInHardLineBreak(nsTextFrame* aFrame, nsBlockFrame* aLineContainer)
 {
-  nsIFrame* lineContainer = FindLineContainer(aFrame);
-  nsBlockFrame* block = do_QueryFrame(lineContainer);
-  if (!block) {
-    // Weird situation where we have a line layout without a block.
-    // No soft breaks occur in this situation.
-    return true;
-  }
   bool foundValidLine;
-  nsBlockInFlowLineIterator iter(block, aFrame, &foundValidLine);
+  nsBlockInFlowLineIterator iter(aLineContainer, aFrame, &foundValidLine);
   if (!foundValidLine) {
     NS_ERROR("Invalid line!");
     return true;
@@ -9662,11 +9655,13 @@ nsTextFrame::GetRenderedText(uint32_t aStartOffset,
 
   // The handling of offsets could be more efficient...
   RenderedText result;
+  nsBlockFrame* lineContainer = nullptr;
   nsTextFrame* textFrame;
   const nsTextFragment* textFrag = mContent->GetText();
   uint32_t offsetInRenderedString = 0;
   bool haveOffsets = false;
 
+  Maybe<nsBlockFrame::AutoLineCursorSetup> autoLineCursor;
   for (textFrame = this; textFrame;
        textFrame = static_cast<nsTextFrame*>(textFrame->GetNextContinuation())) {
     if (textFrame->GetStateBits() & NS_FRAME_IS_DIRTY) {
@@ -9682,10 +9677,30 @@ nsTextFrame::GetRenderedText(uint32_t aStartOffset,
     }
     gfxSkipCharsIterator tmpIter = iter;
 
+    // Whether we need to trim whitespaces after the text frame.
+    bool trimAfter;
+    if (!textFrame->IsAtEndOfLine() ||
+        aTrimTrailingWhitespace !=
+          TrailingWhitespace::TRIM_TRAILING_WHITESPACE) {
+      trimAfter = false;
+    } else if (nsBlockFrame* thisLc =
+               do_QueryFrame(FindLineContainer(textFrame))) {
+      if (thisLc != lineContainer) {
+        // Setup line cursor when needed.
+        lineContainer = thisLc;
+        autoLineCursor.reset();
+        autoLineCursor.emplace(lineContainer);
+      }
+      trimAfter = LineEndsInHardLineBreak(textFrame, lineContainer);
+    } else {
+      // Weird situation where we have a line layout without a block.
+      // No soft breaks occur in this situation.
+      trimAfter = true;
+    }
+
     // Skip to the start of the text run, past ignored chars at start of line
-    TrimmedOffsets trimmedOffsets = textFrame->GetTrimmedOffsets(textFrag,
-       textFrame->IsAtEndOfLine() && LineEndsInHardLineBreak(textFrame) &&
-       aTrimTrailingWhitespace == TrailingWhitespace::TRIM_TRAILING_WHITESPACE);
+    TrimmedOffsets trimmedOffsets =
+        textFrame->GetTrimmedOffsets(textFrag, trimAfter);
     bool trimmedSignificantNewline =
         trimmedOffsets.GetEnd() < GetContentEnd() &&
         HasSignificantTerminalNewline();
diff --git a/mfbt/Attributes.h b/mfbt/Attributes.h
index f7f8a0c39291..df6172f31b5a 100644
--- a/mfbt/Attributes.h
+++ b/mfbt/Attributes.h
@@ -569,4 +569,36 @@
 
 #endif /* __cplusplus */
 
+/**
+ * Printf style formats.  MOZ_FORMAT_PRINTF can be used to annotate a
+ * function or method that is "printf-like"; this will let (some)
+ * compilers check that the arguments match the template string.
+ *
+ * This macro takes two arguments.  The first argument is the argument
+ * number of the template string.  The second argument is the argument
+ * number of the '...' argument holding the arguments.
+ *
+ * Argument numbers start at 1.  Note that the implicit "this"
+ * argument of a non-static member function counts as an argument.
+ *
+ * So, for a simple case like:
+ *   void print_something (int whatever, const char *fmt, ...);
+ * The corresponding annotation would be
+ *   MOZ_FORMAT_PRINTF(2, 3)
+ * However, if "print_something" were a non-static member function,
+ * then the annotation would be:
+ *   MOZ_FORMAT_PRINTF(3, 4)
+ *
+ * Note that the checking is limited to standards-conforming
+ * printf-likes, and in particular this should not be used for
+ * PR_snprintf and friends, which are "printf-like" but which assign
+ * different meanings to the various formats.
+ */
+#ifdef __GNUC__
+#define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck)  \
+    __attribute__ ((format (printf, stringIndex, firstToCheck)))
+#else
+#define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck)
+#endif
+
 #endif /* mozilla_Attributes_h */
diff --git a/mfbt/LinkedList.h b/mfbt/LinkedList.h
index e0f2a03793ae..70641699fb8f 100644
--- a/mfbt/LinkedList.h
+++ b/mfbt/LinkedList.h
@@ -125,34 +125,23 @@ public:
       mIsSentinel(false)
   { }
 
-  LinkedListElement(LinkedListElement<T>&& other)
-    : mIsSentinel(other.mIsSentinel)
+  /*
+   * Moves |aOther| into |*this|. If |aOther| is already in a list, then
+   * |aOther| is removed from the list and replaced by |*this|.
+   */
+  LinkedListElement(LinkedListElement<T>&& aOther)
+    : mIsSentinel(aOther.mIsSentinel)
   {
-    if (!other.isInList()) {
-      mNext = this;
-      mPrev = this;
-      return;
-    }
+    adjustLinkForMove(Move(aOther));
+  }
 
-    MOZ_ASSERT(other.mNext->mPrev == &other);
-    MOZ_ASSERT(other.mPrev->mNext == &other);
-
-    /*
-     * Initialize |this| with |other|'s mPrev/mNext pointers, and adjust those
-     * element to point to this one.
-     */
-    mNext = other.mNext;
-    mPrev = other.mPrev;
-
-    mNext->mPrev = this;
-    mPrev->mNext = this;
-
-    /*
-     * Adjust |other| so it doesn't think it's in a list.  This makes it
-     * safely destructable.
-     */
-    other.mNext = &other;
-    other.mPrev = &other;
+  LinkedListElement& operator=(LinkedListElement<T>&& aOther)
+  {
+    MOZ_ASSERT(mIsSentinel == aOther.mIsSentinel, "Mismatch NodeKind!");
+    MOZ_ASSERT(!isInList(),
+               "Assigning to an element in a list messes up that list!");
+    adjustLinkForMove(Move(aOther));
+    return *this;
   }
 
   ~LinkedListElement()
@@ -233,15 +222,15 @@ public:
 private:
   friend class LinkedList<T>;
 
-  enum NodeKind {
-    NODE_KIND_NORMAL,
-    NODE_KIND_SENTINEL
+  enum class NodeKind {
+    Normal,
+    Sentinel
   };
 
   explicit LinkedListElement(NodeKind nodeKind)
     : mNext(this),
       mPrev(this),
-      mIsSentinel(nodeKind == NODE_KIND_SENTINEL)
+      mIsSentinel(nodeKind == NodeKind::Sentinel)
   { }
 
   /*
@@ -287,7 +276,39 @@ private:
     this->mPrev = listElem;
   }
 
-private:
+  /*
+   * Adjust mNext and mPrev for implementing move constructor and move
+   * assignment.
+   */
+  void adjustLinkForMove(LinkedListElement<T>&& aOther)
+  {
+    if (!aOther.isInList()) {
+      mNext = this;
+      mPrev = this;
+      return;
+    }
+
+    MOZ_ASSERT(aOther.mNext->mPrev == &aOther);
+    MOZ_ASSERT(aOther.mPrev->mNext == &aOther);
+
+    /*
+     * Initialize |this| with |aOther|'s mPrev/mNext pointers, and adjust those
+     * element to point to this one.
+     */
+    mNext = aOther.mNext;
+    mPrev = aOther.mPrev;
+
+    mNext->mPrev = this;
+    mPrev->mNext = this;
+
+    /*
+     * Adjust |aOther| so it doesn't think it's in a list.  This makes it
+     * safely destructable.
+     */
+    aOther.mNext = &aOther;
+    aOther.mPrev = &aOther;
+  }
+
   LinkedListElement& operator=(const LinkedListElement<T>& aOther) = delete;
   LinkedListElement(const LinkedListElement<T>& aOther) = delete;
 };
@@ -319,12 +340,19 @@ public:
     }
   };
 
-  LinkedList() : sentinel(LinkedListElement<T>::NODE_KIND_SENTINEL) { }
+  LinkedList() : sentinel(LinkedListElement<T>::NodeKind::Sentinel) { }
 
   LinkedList(LinkedList<T>&& aOther)
     : sentinel(mozilla::Move(aOther.sentinel))
   { }
 
+  LinkedList& operator=(LinkedList<T>&& aOther)
+  {
+    MOZ_ASSERT(isEmpty(), "Assigning to a non-empty list leaks elements in that list!");
+    sentinel = mozilla::Move(aOther.sentinel);
+    return *this;
+  }
+
   ~LinkedList() {
     MOZ_ASSERT(isEmpty(),
                "failing this assertion means this LinkedList's creator is "
diff --git a/mfbt/Sprintf.h b/mfbt/Sprintf.h
index 39a9ec1317eb..e0be271e5d5c 100644
--- a/mfbt/Sprintf.h
+++ b/mfbt/Sprintf.h
@@ -13,6 +13,7 @@
 #include <stdarg.h>
 
 #include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
 
 #ifdef __cplusplus
 
@@ -26,9 +27,7 @@ int VsprintfLiteral(char (&buffer)[N], const char* format, va_list args)
 }
 
 template <size_t N>
-#if defined(__GNUC__)
-  __attribute__((format(printf, 2, 3)))
-#endif
+MOZ_FORMAT_PRINTF(2, 3)
 int SprintfLiteral(char (&buffer)[N], const char* format, ...)
 {
   va_list args;
diff --git a/mfbt/tests/TestLinkedList.cpp b/mfbt/tests/TestLinkedList.cpp
index 55db35517cbd..519b34c56636 100644
--- a/mfbt/tests/TestLinkedList.cpp
+++ b/mfbt/tests/TestLinkedList.cpp
@@ -12,7 +12,7 @@ using mozilla::LinkedListElement;
 
 struct SomeClass : public LinkedListElement<SomeClass> {
   unsigned int mValue;
-  explicit SomeClass(int aValue) : mValue(aValue) {}
+  explicit SomeClass(int aValue = 0) : mValue(aValue) {}
   void incr() { ++mValue; }
 };
 
@@ -34,7 +34,7 @@ TestList()
   LinkedList<SomeClass> list;
 
   SomeClass one(1), two(2), three(3);
-  
+
   MOZ_RELEASE_ASSERT(list.isEmpty());
   MOZ_RELEASE_ASSERT(!list.getFirst());
   MOZ_RELEASE_ASSERT(!list.getLast());
@@ -52,7 +52,7 @@ TestList()
   MOZ_RELEASE_ASSERT(one.isInList());
   MOZ_RELEASE_ASSERT(!two.isInList());
   MOZ_RELEASE_ASSERT(!three.isInList());
-  
+
   MOZ_RELEASE_ASSERT(!list.isEmpty());
   MOZ_RELEASE_ASSERT(list.getFirst()->mValue == 1);
   MOZ_RELEASE_ASSERT(list.getLast()->mValue == 1);
@@ -117,6 +117,45 @@ TestList()
   MOZ_RELEASE_ASSERT(list.getLast()->mValue == 4);
 }
 
+static void
+TestMove()
+{
+  auto MakeSomeClass =
+    [] (unsigned int aValue) -> SomeClass { return SomeClass(aValue); };
+
+  LinkedList<SomeClass> list1;
+
+  // Test move constructor for LinkedListElement.
+  SomeClass c1(MakeSomeClass(1));
+  list1.insertBack(&c1);
+
+  // Test move assignment for LinkedListElement from an element not in a
+  // list.
+  SomeClass c2;
+  c2 = MakeSomeClass(2);
+  list1.insertBack(&c2);
+
+  // Test move assignment of LinkedListElement from an element already in a
+  // list.
+  SomeClass c3;
+  c3 = Move(c2);
+  MOZ_RELEASE_ASSERT(!c2.isInList());
+  MOZ_RELEASE_ASSERT(c3.isInList());
+
+  // Test move constructor for LinkedList.
+  LinkedList<SomeClass> list2(Move(list1));
+  { unsigned int check[] { 1, 2 }; CheckListValues(list2, check); }
+  MOZ_RELEASE_ASSERT(list1.isEmpty());
+
+  // Test move assignment for LinkedList.
+  LinkedList<SomeClass> list3;
+  list3 = Move(list2);
+  { unsigned int check[] { 1, 2 }; CheckListValues(list3, check); }
+  MOZ_RELEASE_ASSERT(list2.isEmpty());
+
+  list3.clear();
+}
+
 struct PrivateClass : private LinkedListElement<PrivateClass> {
   friend class mozilla::LinkedList<PrivateClass>;
   friend class mozilla::LinkedListElement<PrivateClass>;
@@ -143,5 +182,6 @@ main()
 {
   TestList();
   TestPrivate();
+  TestMove();
   return 0;
 }
diff --git a/moz.configure b/moz.configure
index 58bc27be5c38..43a0503b3879 100644
--- a/moz.configure
+++ b/moz.configure
@@ -316,7 +316,9 @@ def nsis_version(nsis):
         raise FatalCheckError('Unknown version of makensis')
     ver = Version(m.group(0))
 
-    if ver < nsis_min_version:
+    # Versions comparisons don't quite work well with beta versions, so ensure
+    # it works for the non-beta version.
+    if ver < nsis_min_version and (ver >= '3.0a' or ver < '3'):
         raise FatalCheckError('To build the installer you must have NSIS'
                               ' version %s or greater in your path'
                               % nsis_min_version)
diff --git a/python/mozbuild/mozbuild/test/configure/test_moz_configure.py b/python/mozbuild/mozbuild/test/configure/test_moz_configure.py
index 440191c6d7ea..7c318adefd0b 100644
--- a/python/mozbuild/mozbuild/test/configure/test_moz_configure.py
+++ b/python/mozbuild/mozbuild/test/configure/test_moz_configure.py
@@ -57,6 +57,37 @@ class TestMozConfigure(BaseConfigureTest):
                           get_value_for(['--enable-application=browser',
                                          '--with-foo=foo bar']))
 
+    def test_nsis_version(self):
+        this = self
+
+        class FakeNSIS(object):
+            def __init__(self, version):
+                self.version = version
+
+            def __call__(self, stdin, args):
+                this.assertEquals(args, ('-version',))
+                return 0, self.version, ''
+
+        def check_nsis_version(version):
+            sandbox = self.get_sandbox(
+                {'/usr/bin/makensis': FakeNSIS(version)}, {}, [],
+                {'PATH': '/usr/bin', 'MAKENSISU': '/usr/bin/makensis'})
+            return sandbox._value_for(sandbox['nsis_version'])
+
+        with self.assertRaises(SystemExit) as e:
+            check_nsis_version('v2.5')
+
+        with self.assertRaises(SystemExit) as e:
+            check_nsis_version('v3.0a2')
+
+        self.assertEquals(check_nsis_version('v3.0b1'), '3.0b1')
+        self.assertEquals(check_nsis_version('v3.0b2'), '3.0b2')
+        self.assertEquals(check_nsis_version('v3.0rc1'), '3.0rc1')
+        self.assertEquals(check_nsis_version('v3.0'), '3.0')
+        self.assertEquals(check_nsis_version('v3.0-2'), '3.0')
+        self.assertEquals(check_nsis_version('v3.0.1'), '3.0')
+        self.assertEquals(check_nsis_version('v3.1'), '3.1')
+
 
 if __name__ == '__main__':
     main()
diff --git a/security/manager/locales/en-US/chrome/pippki/pippki.properties b/security/manager/locales/en-US/chrome/pippki/pippki.properties
index fe7bc2e0797e..056f609af1fd 100644
--- a/security/manager/locales/en-US/chrome/pippki/pippki.properties
+++ b/security/manager/locales/en-US/chrome/pippki/pippki.properties
@@ -111,7 +111,9 @@ pageInfo_MixedContent2=Parts of the page you are viewing were not encrypted befo
 pageInfo_WeakCipher=Your connection to this website uses weak encryption and is not private. Other people can view your information or modify the website’s behavior.
 
 # Cert Viewer
-certDetails=Certificate Viewer:
+# LOCALIZATION NOTE(certViewerTitle): Title used for the Certificate Viewer.
+# %1$S is a string representative of the certificate being viewed.
+certViewerTitle=Certificate Viewer: “%1$S”
 notPresent=<Not Part Of Certificate>
 
 # Token Manager
diff --git a/security/manager/pki/nsNSSDialogHelper.h b/security/manager/pki/nsNSSDialogHelper.h
index d35646ee9793..87605da5f1d3 100644
--- a/security/manager/pki/nsNSSDialogHelper.h
+++ b/security/manager/pki/nsNSSDialogHelper.h
@@ -11,17 +11,28 @@ class mozIDOMWindowProxy;
 class nsISupports;
 
 /**
- * Common class that uses the window watcher service to open a
- * standard dialog, with or without a parent context. The params
- * parameter can be an nsISupportsArray so any number of additional
- * arguments can be used.
+ * Helper class that uses the window watcher service to open a standard dialog,
+ * with or without a parent context.
  */
 class nsNSSDialogHelper
 {
 public:
-  // params is a nsIDialogParamBlock or a nsIKeygenThread
+  /**
+   * Opens a XUL dialog.
+   *
+   * @param window
+   *        Parent window of the dialog, or nullptr to signal no parent.
+   * @param url
+   *        URL to the XUL dialog.
+   * @param params
+   *        Parameters to pass to the dialog. Same semantics as the
+   *        nsIWindowWatcher.openWindow() |aArguments| parameter.
+   * @param modal
+   *        true if the dialog should be modal, false otherwise.
+   * @return The result of opening the dialog.
+   */
   static nsresult openDialog(mozIDOMWindowProxy* window, const char* url,
                              nsISupports* params, bool modal = true);
 };
 
-#endif
+#endif // nsNSSDialogHelper_h
diff --git a/security/manager/pki/nsNSSDialogs.cpp b/security/manager/pki/nsNSSDialogs.cpp
index fa9bc41e3707..1e80cc4d285c 100644
--- a/security/manager/pki/nsNSSDialogs.cpp
+++ b/security/manager/pki/nsNSSDialogs.cpp
@@ -7,35 +7,28 @@
 /*
  * Dialog services for PIP.
  */
+
+#include "nsNSSDialogs.h"
+
 #include "mozIDOMWindow.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/Casting.h"
 #include "nsArray.h"
-#include "nsDateTimeFormatCID.h"
 #include "nsEmbedCID.h"
-#include "nsIComponentManager.h"
-#include "nsIDateTimeFormat.h"
 #include "nsIDialogParamBlock.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsIInterfaceRequestorUtils.h"
 #include "nsIKeygenThread.h"
 #include "nsIPromptService.h"
 #include "nsIProtectedAuthThread.h"
-#include "nsIServiceManager.h"
 #include "nsIWindowWatcher.h"
 #include "nsIX509CertDB.h"
 #include "nsIX509Cert.h"
-#include "nsIX509CertValidity.h"
 #include "nsNSSDialogHelper.h"
-#include "nsNSSDialogs.h"
-#include "nsPromiseFlatString.h"
-#include "nsReadableUtils.h"
 #include "nsString.h"
 
 #define PIPSTRING_BUNDLE_URL "chrome://pippki/locale/pippki.properties"
 
-/* ==== */
-
 nsNSSDialogs::nsNSSDialogs()
 {
 }
@@ -329,33 +322,18 @@ nsNSSDialogs::GetPKCS12FilePassword(nsIInterfaceRequestor* ctx,
   return NS_OK;
 }
 
-NS_IMETHODIMP 
+NS_IMETHODIMP
 nsNSSDialogs::ViewCert(nsIInterfaceRequestor* ctx, nsIX509Cert* cert)
 {
-  nsCOMPtr<nsIMutableArray> dlgArray = nsArrayBase::Create();
-  if (!dlgArray) {
-    return NS_ERROR_FAILURE;
-  }
-  nsresult rv = dlgArray->AppendElement(cert, false);
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
-  nsCOMPtr<nsIDialogParamBlock> dlgParamBlock(
-    do_CreateInstance(NS_DIALOGPARAMBLOCK_CONTRACTID));
-  if (!dlgParamBlock) {
-    return NS_ERROR_FAILURE;
-  }
-  rv = dlgParamBlock->SetObjects(dlgArray);
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
+  // |ctx| is allowed to be null.
+  NS_ENSURE_ARG(cert);
 
   // Get the parent window for the dialog
   nsCOMPtr<mozIDOMWindowProxy> parent = do_GetInterface(ctx);
   return nsNSSDialogHelper::openDialog(parent,
                                        "chrome://pippki/content/certViewer.xul",
-                                       dlgParamBlock,
-                                       false);
+                                       cert,
+                                       false /*modal*/);
 }
 
 NS_IMETHODIMP
diff --git a/security/manager/pki/resources/content/viewCertDetails.js b/security/manager/pki/resources/content/certViewer.js
similarity index 95%
rename from security/manager/pki/resources/content/viewCertDetails.js
rename to security/manager/pki/resources/content/certViewer.js
index 5a5650a1ebd9..c625076943cf 100644
--- a/security/manager/pki/resources/content/viewCertDetails.js
+++ b/security/manager/pki/resources/content/certViewer.js
@@ -3,6 +3,14 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 "use strict";
 
+/**
+ * @file Implements functionality for certViewer.xul and its tabs certDump.xul
+ *       and viewCertDetails.xul: a dialog that allows various attributes of a
+ *       certificate to be viewed.
+ * @argument {nsISupports} window.arguments[0]
+ *           The cert to view, queryable to nsIX509Cert.
+ */
+
 const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
 const { Services } = Cu.import("resource://gre/modules/Services.jsm", {});
 
@@ -16,7 +24,6 @@ const nsIASN1Sequence = Ci.nsIASN1Sequence;
 const nsIASN1PrintableItem = Ci.nsIASN1PrintableItem;
 const nsIASN1Tree = Ci.nsIASN1Tree;
 const nsASN1Tree = "@mozilla.org/security/nsASN1Tree;1";
-const nsIDialogParamBlock = Ci.nsIDialogParamBlock;
 
 var bundle;
 
@@ -71,21 +78,11 @@ function AddUsage(usage)
 
 function setWindowName()
 {
-  //  Get the cert from the cert database
-  var certdb = Components.classes[nsX509CertDB].getService(nsIX509CertDB);
-  var myName = self.name;
   bundle = document.getElementById("pippki_bundle");
-  var cert;
 
-  var certDetails = bundle.getString('certDetails');
-  if (myName != "") {
-    document.title = certDetails + '"' + myName + '"'; // XXX l10n?
-    cert = certdb.findCertByNickname(myName);
-  } else {
-    var params = window.arguments[0].QueryInterface(nsIDialogParamBlock);
-    cert = params.objects.queryElementAt(0, nsIX509Cert);
-    document.title = certDetails + '"' + cert.windowTitle + '"'; // XXX l10n?
-  }
+  let cert = window.arguments[0].QueryInterface(Ci.nsIX509Cert);
+  document.title = bundle.getFormattedString("certViewerTitle",
+                                             [cert.windowTitle]);
 
   //
   //  Set the cert attributes for viewing
diff --git a/security/manager/pki/resources/content/certViewer.xul b/security/manager/pki/resources/content/certViewer.xul
index e9a1e2b77fcc..3f2cd3bde04f 100644
--- a/security/manager/pki/resources/content/certViewer.xul
+++ b/security/manager/pki/resources/content/certViewer.xul
@@ -20,7 +20,8 @@
 
 <stringbundle id="pippki_bundle" src="chrome://pippki/locale/pippki.properties"/>
 
-<script type="application/javascript" src="chrome://pippki/content/viewCertDetails.js"/>
+<script type="application/javascript"
+        src="chrome://pippki/content/certViewer.js"/>
 <script type="application/javascript" src="chrome://pippki/content/pippki.js"/>
 
   <tabbox flex="1">
diff --git a/security/manager/pki/resources/jar.mn b/security/manager/pki/resources/jar.mn
index 4ef3d4f2a808..6c1c4af27542 100644
--- a/security/manager/pki/resources/jar.mn
+++ b/security/manager/pki/resources/jar.mn
@@ -24,12 +24,12 @@ pippki.jar:
     content/pippki/exceptionDialog.js        (content/exceptionDialog.js)
     content/pippki/deletecert.xul            (content/deletecert.xul)
     content/pippki/deletecert.js             (content/deletecert.js)
-    content/pippki/viewCertDetails.js        (content/viewCertDetails.js)
     content/pippki/setp12password.xul        (content/setp12password.xul)
     content/pippki/pippki.js                 (content/pippki.js)
     content/pippki/clientauthask.xul	     (content/clientauthask.xul)
     content/pippki/clientauthask.js          (content/clientauthask.js)
     content/pippki/certViewer.xul            (content/certViewer.xul)
+    content/pippki/certViewer.js             (content/certViewer.js)
     content/pippki/certDump.xul              (content/certDump.xul)
     content/pippki/device_manager.xul        (content/device_manager.xul)
     content/pippki/device_manager.js         (content/device_manager.js)
diff --git a/security/manager/ssl/tests/mochitest/browser/browser_certViewer.js b/security/manager/ssl/tests/mochitest/browser/browser_certViewer.js
index bd9e179ce788..ec777361eb2b 100644
--- a/security/manager/ssl/tests/mochitest/browser/browser_certViewer.js
+++ b/security/manager/ssl/tests/mochitest/browser/browser_certViewer.js
@@ -10,42 +10,47 @@
 
 var { OS } = Cu.import("resource://gre/modules/osfile.jsm", {});
 
-add_task(function* () {
+add_task(function* testCAandTitle() {
   let cert = yield readCertificate("ca.pem", "CTu,CTu,CTu");
   let win = yield displayCertificate(cert);
   checkUsages(win, ["SSL Certificate Authority"]);
+
+  // There's no real need to test the title for every cert, so we just test it
+  // once here.
+  Assert.equal(win.document.title, "Certificate Viewer: \u201Cca\u201D",
+               "Actual and expected title should match");
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testSSLEndEntity() {
   let cert = yield readCertificate("ssl-ee.pem", ",,");
   let win = yield displayCertificate(cert);
   checkUsages(win, ["SSL Server Certificate", "SSL Client Certificate"]);
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testEmailEndEntity() {
   let cert = yield readCertificate("email-ee.pem", ",,");
   let win = yield displayCertificate(cert);
   checkUsages(win, ["Email Recipient Certificate", "Email Signer Certificate"]);
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testCodeSignEndEntity() {
   let cert = yield readCertificate("code-ee.pem", ",,");
   let win = yield displayCertificate(cert);
   checkUsages(win, ["Object Signer"]);
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testExpired() {
   let cert = yield readCertificate("expired-ca.pem", ",,");
   let win = yield displayCertificate(cert);
   checkError(win, "Could not verify this certificate because it has expired.");
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testIssuerExpired() {
   let cert = yield readCertificate("ee-from-expired-ca.pem", ",,");
   let win = yield displayCertificate(cert);
   checkError(win,
@@ -54,7 +59,7 @@ add_task(function* () {
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testUnknownIssuer() {
   let cert = yield readCertificate("unknown-issuer.pem", ",,");
   let win = yield displayCertificate(cert);
   checkError(win,
@@ -63,7 +68,7 @@ add_task(function* () {
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testInsecureAlgo() {
   let cert = yield readCertificate("md5-ee.pem", ",,");
   let win = yield displayCertificate(cert);
   checkError(win,
@@ -73,7 +78,7 @@ add_task(function* () {
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testUntrusted() {
   let cert = yield readCertificate("untrusted-ca.pem", "p,p,p");
   let win = yield displayCertificate(cert);
   checkError(win,
@@ -81,7 +86,7 @@ add_task(function* () {
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testUntrustedIssuer() {
   let cert = yield readCertificate("ee-from-untrusted-ca.pem", ",,");
   let win = yield displayCertificate(cert);
   checkError(win,
@@ -90,7 +95,7 @@ add_task(function* () {
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testRevoked() {
   // Note that there's currently no way to un-do this. This should only be a
   // problem if another test re-uses a certificate with this same key (perhaps
   // likely) and subject (less likely).
@@ -106,7 +111,7 @@ add_task(function* () {
   yield BrowserTestUtils.closeWindow(win);
 });
 
-add_task(function* () {
+add_task(function* testInvalid() {
   // This certificate has a keyUsage extension asserting cRLSign and
   // keyCertSign, but it doesn't have a basicConstraints extension. This
   // shouldn't be valid for any usage. Sadly, we give a pretty lame error
@@ -129,13 +134,8 @@ add_task(function* () {
  *         viewer window when the usages have been determined.
  */
 function displayCertificate(certificate) {
-  let array = Cc["@mozilla.org/array;1"].createInstance(Ci.nsIMutableArray);
-  array.appendElement(certificate, false);
-  let params = Cc["@mozilla.org/embedcomp/dialogparam;1"]
-                 .createInstance(Ci.nsIDialogParamBlock);
-  params.objects = array;
   let win = window.openDialog("chrome://pippki/content/certViewer.xul", "",
-                              "", params);
+                              "", certificate);
   return TestUtils.topicObserved("ViewCertDetails:CertUsagesDone",
                                  (subject, data) => subject == win)
   .then(([subject, data]) => subject, error => { throw error; });
diff --git a/taskcluster/ci/desktop-test/test-platforms.yml b/taskcluster/ci/desktop-test/test-platforms.yml
index 618afed7b297..f6e4fa081c0a 100644
--- a/taskcluster/ci/desktop-test/test-platforms.yml
+++ b/taskcluster/ci/desktop-test/test-platforms.yml
@@ -25,9 +25,42 @@ linux64-pgo/opt:
 linux64-asan/opt:
     build-platform: linux64-asan/opt
     test-set: asan-tests
+
 linux64-ccov/opt:
     build-platform: linux64-ccov/opt
     test-set: ccov-code-coverage-tests
 linux64-jsdcov/opt:
     build-platform: linux64-jsdcov/opt
-    test-set: jsdcov-code-coverage-tests
\ No newline at end of file
+    test-set: jsdcov-code-coverage-tests
+
+# win32 vm
+windows7-32-vm/debug:
+    build-platform: win32/debug
+    test-set: windows-vm-tests
+windows7-32-vm/opt:
+    build-platform: win32/opt
+    test-set: windows-vm-tests
+
+# win32 gpu
+#windows7-32/debug:
+#    build-platform: win32/debug
+#    test-set: windows-gpu-tests
+#windows7-32/opt:
+#    build-platform: win32/opt
+#    test-set: windows-gpu-tests
+
+# win64 vm
+windows10-64-vm/debug:
+    build-platform: win64/debug
+    test-set: windows-vm-tests
+windows10-64-vm/opt:
+    build-platform: win64/opt
+    test-set: windows-vm-tests
+
+# win64 gpu
+#windows10-64/debug:
+#    build-platform: win64/debug
+#    test-set: windows-gpu-tests
+#windows10-64/opt:
+#    build-platform: win64/opt
+#    test-set: windows-gpu-tests
diff --git a/taskcluster/ci/desktop-test/test-sets.yml b/taskcluster/ci/desktop-test/test-sets.yml
index d8ea65e7b966..b2f2d2e73d6b 100644
--- a/taskcluster/ci/desktop-test/test-sets.yml
+++ b/taskcluster/ci/desktop-test/test-sets.yml
@@ -58,6 +58,35 @@ asan-tests:
     - reftest-no-accel
     - xpcshell
 
+windows-vm-tests:
+    - cppunit
+    #- crashtest
+    #- external-media-tests
+    #- gtest
+    #- jittest
+    #- jsreftest
+    #- marionette
+    #- mochitest
+    #- mochitest-browser-chrome
+    #- mochitest-devtools-chrome
+    #- mochitest-jetpack
+    #- mochitest-media
+    #- web-platform-tests
+    #- web-platform-tests-reftests
+    #- xpcshell
+
+# windows-gpu-tests:
+#    - reftest
+#    - reftest-no-accel
+#    - mochitest-webgl
+
+# these tests currently run on hardware, but may migrate above when validated
+# note: on win, mochitest-a11y and mochitest-chrome come under mochitest-other
+# windows-hw-tests:
+#    - mochitest-clipboard
+#    - mochitest-gpu
+#    - mochitest-other
+
 ccov-code-coverage-tests:
     - mochitest-browser-chrome
 
diff --git a/taskcluster/ci/desktop-test/tests.yml b/taskcluster/ci/desktop-test/tests.yml
index 3ec0f4e56c54..b4310435836f 100644
--- a/taskcluster/ci/desktop-test/tests.yml
+++ b/taskcluster/ci/desktop-test/tests.yml
@@ -15,11 +15,8 @@ cppunit:
         no-read-buildbot-config: true
         config:
             by-test-platform:
-                # Coming soon:
-                # win.*:
-                #    - unittests/win_unittest.py
-                #    - remove_executables.py
-                # ...
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -31,12 +28,19 @@ crashtest:
     suite: reftest/crashtest
     treeherder-symbol: tc-R(C)
     docker-image: {"in-tree": "desktop1604-test"}
+    e10s:
+        by-test-platform:
+            # Bug 1304435
+            win.*: false
+            default: both
     mozharness:
         script: desktop_unittest.py
         chunked: true
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -54,8 +58,12 @@ external-media-tests:
         script: firefox_media_tests_buildbot.py
         no-read-buildbot-config: true
         config:
-            - mediatests/buildbot_posix_config.py
-            - remove_executables.py
+            by-test-platform:
+                win.*:
+                    - mediatests/taskcluster_windows_config.py
+                default:
+                    - mediatests/buildbot_posix_config.py
+                    - remove_executables.py
 
 firefox-ui-functional-local:
     description: "Firefox-ui-tests functional run"
@@ -98,6 +106,8 @@ gtest:
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -109,12 +119,17 @@ jittest:
     suite: jittest/jittest-chunked
     treeherder-symbol: tc(Jit)
     e10s: false
-    chunks: 6
+    chunks:
+        by-test-platform:
+            win.*: 1
+            default: 6
     mozharness:
         script: desktop_unittest.py
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -125,12 +140,17 @@ jsreftest:
     description: "JS Reftest run"
     suite: reftest/jsreftest
     treeherder-symbol: tc-R(J)
-    chunks: 2
+    chunks:
+        by-test-platform:
+            win.*: 1
+            default: 2
     mozharness:
         script: desktop_unittest.py
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -146,15 +166,22 @@ marionette:
         script: marionette.py
         no-read-buildbot-config: true
         config:
-            - marionette/prod_config.py
-            - remove_executables.py
+            by-test-platform:
+                win.*:
+                    - marionette/windows_taskcluster_config.py
+                default:
+                    - marionette/prod_config.py
+                    - remove_executables.py
 
 mochitest:
     description: "Mochitest plain run"
     suite: mochitest/plain-chunked
     treeherder-symbol: tc-M()
     loopback-video: true
-    chunks: 10
+    chunks:
+        by-test-platform:
+            win.*: 5
+            default: 10
     max-run-time: 5400
     mozharness:
         script: desktop_unittest.py
@@ -162,6 +189,8 @@ mochitest:
         chunked: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -183,6 +212,8 @@ mochitest-a11y:
         chunked: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -222,6 +253,8 @@ mochitest-browser-chrome:
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -254,6 +287,8 @@ mochitest-chrome:
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -272,6 +307,8 @@ mochitest-clipboard:
         chunked: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -284,7 +321,10 @@ mochitest-devtools-chrome:
     treeherder-symbol: tc-M(dt)
     loopback-video: true
     max-run-time: 5400
-    chunks: 10
+    chunks:
+        by-test-platform:
+            win.*: 8
+            default: 10
     e10s:
         by-test-platform:
             # Bug 1242986: linux64/debug mochitest-devtools-chrome e10s is not greened up yet
@@ -295,6 +335,8 @@ mochitest-devtools-chrome:
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -313,12 +355,18 @@ mochitest-gpu:
     suite: mochitest/plain-gpu,chrome-gpu,browser-chrome-gpu
     treeherder-symbol: tc-M(gpu)
     loopback-video: true
+    e10s:
+        by-test-platform:
+            win.*: both
+            default: true
     mozharness:
         script: desktop_unittest.py
         no-read-buildbot-config: true
         chunked: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -338,11 +386,14 @@ mochitest-jetpack:
         chunked: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
         extra-options:
             - --mochitest-suite=jetpack-package
+            - --mochitest-suite=jetpack-addon
 
 mochitest-media:
     description: "Mochitest media run"
@@ -358,6 +409,8 @@ mochitest-media:
         chunked: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -376,6 +429,8 @@ mochitest-webgl:
         chunked: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -395,6 +450,8 @@ reftest:
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -412,6 +469,8 @@ reftest-no-accel:
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
@@ -431,8 +490,12 @@ web-platform-tests:
         script: web_platform_tests.py
         no-read-buildbot-config: true
         config:
-            - web_platform_tests/prod_config.py
-            - remove_executables.py
+            by-test-platform:
+                win.*:
+                    - web_platform_tests/prod_config_windows_taskcluster.py
+                default:
+                    - web_platform_tests/prod_config.py
+                    - remove_executables.py
         extra-options:
             - --test-type=testharness
 
@@ -448,8 +511,12 @@ web-platform-tests-reftests:
         script: web_platform_tests.py
         no-read-buildbot-config: true
         config:
-            - web_platform_tests/prod_config.py
-            - remove_executables.py
+            by-test-platform:
+                win.*:
+                    - web_platform_tests/prod_config_windows_taskcluster.py
+                default:
+                    - web_platform_tests/prod_config.py
+                    - remove_executables.py
         extra-options:
             - --test-type=reftest
 
@@ -465,8 +532,12 @@ web-platform-tests-wdspec:
         script: web_platform_tests.py
         no-read-buildbot-config: true
         config:
-            - web_platform_tests/prod_config.py
-            - remove_executables.py
+            by-test-platform:
+                win.*:
+                    - web_platform_tests/prod_config_windows_taskcluster.py
+                default:
+                    - web_platform_tests/prod_config.py
+                    - remove_executables.py
         extra-options:
             - --test-type=wdspec
 
@@ -476,6 +547,7 @@ xpcshell:
     treeherder-symbol: tc-X()
     chunks:
         by-test-platform:
+            # win.*: 1
             linux64/debug: 10
             default: 8
     max-run-time: 5400
@@ -485,6 +557,8 @@ xpcshell:
         no-read-buildbot-config: true
         config:
             by-test-platform:
+                win.*:
+                    - unittests/win_taskcluster_unittest.py
                 default:
                     - unittests/linux_unittest.py
                     - remove_executables.py
diff --git a/taskcluster/taskgraph/transforms/task.py b/taskcluster/taskgraph/transforms/task.py
index f63a7d1a5e71..76b62fae7a41 100644
--- a/taskcluster/taskgraph/transforms/task.py
+++ b/taskcluster/taskgraph/transforms/task.py
@@ -205,7 +205,7 @@ task_description_schema = Schema({
         Required('implementation'): 'generic-worker',
 
         # command is a list of commands to run, sequentially
-        'command': [basestring],
+        'command': [taskref_or_string],
 
         # artifacts to extract from the task image after completion; note that artifacts
         # for the generic worker cannot have names
@@ -222,6 +222,9 @@ task_description_schema = Schema({
 
         # the maximum time to run, in seconds
         'max-run-time': int,
+
+        # os user groups for test task workers
+        Optional('os-groups', default=[]): [basestring],
     }, {
         Required('implementation'): 'buildbot-bridge',
 
@@ -400,8 +403,9 @@ def build_generic_worker_payload(config, task, task_def):
     task_def['payload'] = {
         'command': worker['command'],
         'artifacts': artifacts,
-        'env': worker['env'],
+        'env': worker.get('env', {}),
         'maxRunTime': worker['max-run-time'],
+        'osGroups': worker.get('os-groups', []),
     }
 
     if 'retry-exit-status' in worker:
diff --git a/taskcluster/taskgraph/transforms/tests/all_kinds.py b/taskcluster/taskgraph/transforms/tests/all_kinds.py
index b892059aed94..ae0261f121bd 100644
--- a/taskcluster/taskgraph/transforms/tests/all_kinds.py
+++ b/taskcluster/taskgraph/transforms/tests/all_kinds.py
@@ -24,8 +24,10 @@ transforms = TransformSequence()
 def set_worker_implementation(config, tests):
     """Set the worker implementation based on the test platform."""
     for test in tests:
-        # this is simple for now, but soon will not be!
-        test['worker-implementation'] = 'docker-worker'
+        if test['test-platform'].startswith('win'):
+            test['worker-implementation'] = 'generic-worker'
+        else:
+            test['worker-implementation'] = 'docker-worker'
         yield test
 
 
diff --git a/taskcluster/taskgraph/transforms/tests/desktop_test.py b/taskcluster/taskgraph/transforms/tests/desktop_test.py
index 3ddac0d167fd..6053efac7c14 100644
--- a/taskcluster/taskgraph/transforms/tests/desktop_test.py
+++ b/taskcluster/taskgraph/transforms/tests/desktop_test.py
@@ -35,11 +35,12 @@ def set_treeherder_machine_platform(config, tests):
     # platforms
     translation = {
         'linux64-asan/opt': 'linux64/asan',
-        'linux64-pgo/opt': 'linux64/pgo',
+        'linux64-pgo/opt': 'linux64/pgo'
     }
     for test in tests:
         build_platform = test['build-platform']
-        test['treeherder-machine-platform'] = translation.get(build_platform, build_platform)
+        test_platform = test['test-platform']
+        test['treeherder-machine-platform'] = translation.get(build_platform, test_platform)
         yield test
 
 
@@ -83,7 +84,11 @@ def split_e10s(config, tests):
 @transforms.add
 def allow_software_gl_layers(config, tests):
     for test in tests:
-        allow = get_keyed_by(item=test, field='allow-software-gl-layers',
+
+        # since this value defaults to true, but is not applicable on windows,
+        # it's overriden for that platform here.
+        allow = not test['test-platform'].startswith('win') \
+            and get_keyed_by(item=test, field='allow-software-gl-layers',
                              item_name=test['test-name'])
         if allow:
             assert test['instance-size'] != 'legacy',\
@@ -94,3 +99,13 @@ def allow_software_gl_layers(config, tests):
                               .append("--allow-software-gl-layers")
 
         yield test
+
+
+@transforms.add
+def add_os_groups(config, tests):
+    for test in tests:
+        if test['test-platform'].startswith('win'):
+            groups = get_keyed_by(item=test, field='os-groups', item_name=test['test-name'])
+            if groups:
+                test['os-groups'] = groups
+        yield test
diff --git a/taskcluster/taskgraph/transforms/tests/make_task_description.py b/taskcluster/taskgraph/transforms/tests/make_task_description.py
index 7916289a6deb..2a305c9122df 100644
--- a/taskcluster/taskgraph/transforms/tests/make_task_description.py
+++ b/taskcluster/taskgraph/transforms/tests/make_task_description.py
@@ -27,13 +27,18 @@ from taskgraph.transforms.job.common import (
 import logging
 
 ARTIFACT_URL = 'https://queue.taskcluster.net/v1/task/{}/artifacts/{}'
-
-ARTIFACTS = [
-    # (artifact name prefix, in-image path)
-    ("public/logs/", "/home/worker/workspace/build/upload/logs/"),
-    ("public/test", "/home/worker/artifacts/"),
-    ("public/test_info/", "/home/worker/workspace/build/blobber_upload_dir/"),
-]
+WORKER_TYPE = {
+    # default worker types keyed by instance-size
+    'large': 'aws-provisioner-v1/desktop-test-large',
+    'xlarge': 'aws-provisioner-v1/desktop-test-xlarge',
+    'legacy': 'aws-provisioner-v1/desktop-test',
+    'default': 'aws-provisioner-v1/desktop-test-large',
+    # windows worker types keyed by test-platform
+    'windows7-32-vm': 'aws-provisioner-v1/gecko-t-win7-32',
+    'windows7-32': 'aws-provisioner-v1/gecko-t-win7-32-gpu',
+    'windows10-64-vm': 'aws-provisioner-v1/gecko-t-win10-64',
+    'windows10-64': 'aws-provisioner-v1/gecko-t-win10-64-gpu'
+}
 
 logger = logging.getLogger(__name__)
 
@@ -122,6 +127,13 @@ def worker_setup_function(name):
 @worker_setup_function("docker-engine")
 @worker_setup_function("docker-worker")
 def docker_worker_setup(config, test, taskdesc):
+
+    artifacts = [
+        # (artifact name prefix, in-image path)
+        ("public/logs/", "/home/worker/workspace/build/upload/logs/"),
+        ("public/test", "/home/worker/artifacts/"),
+        ("public/test_info/", "/home/worker/workspace/build/blobber_upload_dir/"),
+    ]
     mozharness = test['mozharness']
 
     installer_url = ARTIFACT_URL.format('<build>', mozharness['build-artifact-name'])
@@ -130,12 +142,7 @@ def docker_worker_setup(config, test, taskdesc):
     mozharness_url = ARTIFACT_URL.format('<build>',
                                          'public/build/mozharness.zip')
 
-    taskdesc['worker-type'] = {
-        'default': 'aws-provisioner-v1/desktop-test-large',
-        'large': 'aws-provisioner-v1/desktop-test-large',
-        'xlarge': 'aws-provisioner-v1/desktop-test-xlarge',
-        'legacy': 'aws-provisioner-v1/desktop-test',
-    }[test['instance-size']]
+    taskdesc['worker-type'] = WORKER_TYPE[test['instance-size']]
 
     worker = taskdesc['worker'] = {}
     worker['implementation'] = test['worker-implementation']
@@ -152,7 +159,7 @@ def docker_worker_setup(config, test, taskdesc):
         'name': prefix,
         'path': path,
         'type': 'directory',
-    } for (prefix, path) in ARTIFACTS]
+    } for (prefix, path) in artifacts]
 
     worker['caches'] = [{
         'type': 'persistent',
@@ -242,3 +249,111 @@ def docker_worker_setup(config, test, taskdesc):
         command.append('--download-symbols=' + download_symbols)
 
     worker['command'] = command
+
+
+def normpath(path):
+    return path.replace('/', '\\')
+
+
+def get_firefox_version():
+    with open('browser/config/version.txt', 'r') as f:
+        return f.readline().strip()
+
+
+@worker_setup_function('generic-worker')
+def generic_worker_setup(config, test, taskdesc):
+    artifacts = [
+        {
+            'path': 'public\\logs\\localconfig.json',
+            'type': 'file'
+        },
+        {
+            'path': 'public\\logs\\log_critical.log',
+            'type': 'file'
+        },
+        {
+            'path': 'public\\logs\\log_error.log',
+            'type': 'file'
+        },
+        {
+            'path': 'public\\logs\\log_fatal.log',
+            'type': 'file'
+        },
+        {
+            'path': 'public\\logs\\log_info.log',
+            'type': 'file'
+        },
+        {
+            'path': 'public\\logs\\log_raw.log',
+            'type': 'file'
+        },
+        {
+            'path': 'public\\logs\\log_warning.log',
+            'type': 'file'
+        },
+        {
+            'path': 'public\\test_info',
+            'type': 'directory'
+        }
+    ]
+    mozharness = test['mozharness']
+
+    build_platform = taskdesc['attributes']['build_platform']
+    test_platform = test['test-platform'].split('/')[0]
+
+    target = 'firefox-{}.en-US.{}'.format(get_firefox_version(), build_platform)
+
+    installer_url = ARTIFACT_URL.format(
+        '<build>', 'public/build/{}.zip'.format(target))
+    test_packages_url = ARTIFACT_URL.format(
+        '<build>', 'public/build/{}.test_packages.json'.format(target))
+    mozharness_url = ARTIFACT_URL.format(
+        '<build>', 'public/build/mozharness.zip')
+
+    taskdesc['worker-type'] = WORKER_TYPE[test_platform]
+
+    taskdesc['scopes'].extend(
+        ['generic-worker:os-group:{}'.format(group) for group in test['os-groups']])
+
+    worker = taskdesc['worker'] = {}
+    worker['os-groups'] = test['os-groups']
+    worker['implementation'] = test['worker-implementation']
+    worker['max-run-time'] = test['max-run-time']
+    worker['artifacts'] = artifacts
+
+    env = worker['env'] = {
+        # Bug 1306989
+        'APPDATA': '%cd%\\AppData\\Roaming',
+        'LOCALAPPDATA': '%cd%\\AppData\\Local',
+        'TEMP': '%cd%\\AppData\\Local\\Temp',
+        'TMP': '%cd%\\AppData\\Local\\Temp',
+        'USERPROFILE': '%cd%',
+    }
+
+    # assemble the command line
+    mh_command = [
+        'c:\\mozilla-build\\python\\python.exe',
+        '-u',
+        'mozharness\\scripts\\' + normpath(mozharness['script'])
+    ]
+    for mh_config in mozharness['config']:
+        mh_command.extend(['--cfg', 'mozharness\\configs\\' + normpath(mh_config)])
+    mh_command.extend(mozharness.get('extra-options', []))
+    if mozharness.get('no-read-buildbot-config'):
+        mh_command.append('--no-read-buildbot-config')
+    mh_command.extend(['--installer-url', installer_url])
+    mh_command.extend(['--test-packages-url', test_packages_url])
+    if mozharness.get('download-symbols'):
+        if isinstance(mozharness['download-symbols'], basestring):
+            mh_command.extend(['--download-symbols', mozharness['download-symbols']])
+        else:
+            mh_command.extend(['--download-symbols', 'true'])
+
+    worker['command'] = [
+        'mkdir {} {}'.format(env['APPDATA'], env['TMP']),
+        {'task-reference': 'c:\\mozilla-build\\wget\\wget.exe {}'.format(mozharness_url)},
+        'c:\\mozilla-build\\info-zip\\unzip.exe mozharness.zip',
+        {'task-reference': ' '.join(mh_command)},
+        'xcopy build\\blobber_upload_dir public\\test_info /e /i',
+        'copy /y logs\\*.* public\\logs\\'
+    ]
diff --git a/taskcluster/taskgraph/transforms/tests/test_description.py b/taskcluster/taskgraph/transforms/tests/test_description.py
index e514479c0a09..aa99f7534c7d 100644
--- a/taskcluster/taskgraph/transforms/tests/test_description.py
+++ b/taskcluster/taskgraph/transforms/tests/test_description.py
@@ -106,8 +106,8 @@ test_description_schema = Schema({
     # test platform.
     Optional('worker-implementation'): Any(
         'docker-worker',
-        # coming soon:
         'generic-worker',
+        # coming soon:
         'docker-engine',
         'buildbot-bridge',
     ),
@@ -199,6 +199,14 @@ test_description_schema = Schema({
     # The current chunk; this is filled in by `all_kinds.py`
     Optional('this-chunk'): int,
 
+    # os user groups for test task workers; required scopes, will be
+    # added automatically
+    Optional('os-groups', default=[]): Any(
+        [basestring],
+        # todo: create a dedicated elevated worker group and name here
+        {'by-test-platform': {basestring: [basestring]}},
+    ),
+
     # -- values supplied by the task-generation infrastructure
 
     # the platform of the build this task is testing
diff --git a/testing/mozharness/configs/marionette/windows_taskcluster_config.py b/testing/mozharness/configs/marionette/windows_taskcluster_config.py
new file mode 100644
index 000000000000..02262e4db537
--- /dev/null
+++ b/testing/mozharness/configs/marionette/windows_taskcluster_config.py
@@ -0,0 +1,122 @@
+# This is a template config file for marionette production on Windows.
+import os
+import sys
+
+config = {
+    # marionette options
+    "marionette_address": "localhost:2828",
+    "test_manifest": "unit-tests.ini",
+
+    "virtualenv_python_dll": os.path.join(os.path.dirname(sys.executable), 'python27.dll'),
+    "virtualenv_path": 'venv',
+    "exes": {
+        'python': sys.executable,
+        'virtualenv': [
+            sys.executable,
+            os.path.join(os.path.dirname(sys.executable), 'Lib', 'site-packages', 'virtualenv.py')
+        ],
+        'mozinstall': ['build/venv/scripts/python', 'build/venv/scripts/mozinstall-script.py'],
+        'tooltool.py': [sys.executable, os.path.join(os.environ['MOZILLABUILD'], 'tooltool.py')],
+        'hg': os.path.join(os.environ['PROGRAMFILES'], 'Mercurial', 'hg')
+    },
+
+    "find_links": [
+        "http://pypi.pvt.build.mozilla.org/pub",
+        "http://pypi.pub.build.mozilla.org/pub",
+    ],
+    "pip_index": False,
+
+    "default_actions": [
+        'clobber',
+        'download-and-extract',
+        'create-virtualenv',
+        'install',
+        'run-tests',
+    ],
+    "default_blob_upload_servers": [
+         "https://blobupload.elasticbeanstalk.com",
+    ],
+    "blob_uploader_auth_file" : 'C:/builds/oauth.txt',
+    "download_minidump_stackwalk": True,
+    "download_symbols": "ondemand",
+    "suite_definitions": {
+        "gaiatest_desktop": {
+            "options": [
+                "--restart",
+                "--timeout=%(timeout)s",
+                "--testvars=%(testvars)s",
+                "--profile=%(profile)s",
+                "--symbols-path=%(symbols_path)s",
+                "--gecko-log=%(gecko_log)s",
+                "--log-xunit=%(xml_output)s",
+                "--html-output=%(html_output)s",
+                "--log-raw=%(raw_log_file)s",
+                "--log-errorsummary=%(error_summary_file)s",
+                "--binary=%(binary)s",
+                "--address=%(address)s",
+                "--total-chunks=%(total_chunks)s",
+                "--this-chunk=%(this_chunk)s"
+            ],
+            "run_filename": "",
+            "testsdir": ""
+        },
+        "gaiatest_emulator": {
+            "options": [
+                "--restart",
+                "--timeout=%(timeout)s",
+                "--testvars=%(testvars)s",
+                "--profile=%(profile)s",
+                "--symbols-path=%(symbols_path)s",
+                "--log-xunit=%(xml_output)s",
+                "--html-output=%(html_output)s",
+                "--log-raw=%(raw_log_file)s",
+                "--log-errorsummary=%(error_summary_file)s",
+                "--logcat-dir=%(logcat_dir)s",
+                "--emulator=%(emulator)s",
+                "--homedir=%(homedir)s"
+            ],
+            "run_filename": "",
+            "testsdir": ""
+        },
+        "marionette_desktop": {
+            "options": [
+                "--log-raw=%(raw_log_file)s",
+                "--log-errorsummary=%(error_summary_file)s",
+                "--binary=%(binary)s",
+                "--address=%(address)s",
+                "--symbols-path=%(symbols_path)s"
+            ],
+            "run_filename": "",
+            "testsdir": ""
+        },
+        "marionette_emulator": {
+            "options": [
+                "--log-raw=%(raw_log_file)s",
+                "--log-errorsummary=%(error_summary_file)s",
+                "--logcat-dir=%(logcat_dir)s",
+                "--emulator=%(emulator)s",
+                "--homedir=%(homedir)s",
+                "--symbols-path=%(symbols_path)s"
+            ],
+            "run_filename": "",
+            "testsdir": ""
+        },
+        "webapi_desktop": {
+            "options": [],
+            "run_filename": "",
+            "testsdir": ""
+        },
+        "webapi_emulator": {
+            "options": [
+                "--log-raw=%(raw_log_file)s",
+                "--log-errorsummary=%(error_summary_file)s",
+                "--symbols-path=%(symbols_path)s",
+                "--logcat-dir=%(logcat_dir)s",
+                "--emulator=%(emulator)s",
+                "--homedir=%(homedir)s"
+            ],
+            "run_filename": "",
+            "testsdir": ""
+        }
+    },
+}
diff --git a/testing/mozharness/configs/mediatests/taskcluster_windows_config.py b/testing/mozharness/configs/mediatests/taskcluster_windows_config.py
new file mode 100644
index 000000000000..4a850d0623b4
--- /dev/null
+++ b/testing/mozharness/configs/mediatests/taskcluster_windows_config.py
@@ -0,0 +1,54 @@
+import os
+import sys
+import mozharness
+
+external_tools_path = os.path.join(
+    os.path.abspath(os.path.dirname(os.path.dirname(mozharness.__file__))),
+    'external_tools',
+)
+
+config = {
+    "virtualenv_python_dll": os.path.join(os.path.dirname(sys.executable), 'python27.dll'),
+    "virtualenv_path": 'venv',
+    "exes": {
+        'python': sys.executable,
+        'virtualenv': [
+            sys.executable,
+            os.path.join(os.path.dirname(sys.executable), 'Lib', 'site-packages', 'virtualenv.py')
+        ],
+        'mozinstall': ['build/venv/scripts/python', 'build/venv/scripts/mozinstall-script.py'],
+        'tooltool.py': [sys.executable, os.path.join(os.environ['MOZILLABUILD'], 'tooltool.py')],
+        'hg': os.path.join(os.environ['PROGRAMFILES'], 'Mercurial', 'hg')
+    },
+    "find_links": [
+        "http://pypi.pvt.build.mozilla.org/pub",
+        "http://pypi.pub.build.mozilla.org/pub",
+    ],
+    "pip_index": False,
+
+    "default_actions": [
+        'clobber',
+        'download-and-extract',
+        'create-virtualenv',
+        'install',
+        'run-media-tests',
+    ],
+    "default_blob_upload_servers": [
+         "https://blobupload.elasticbeanstalk.com",
+    ],
+    "blob_uploader_auth_file" : 'C:/builds/oauth.txt',
+    "in_tree_config": "config/mozharness/marionette.py",
+    "download_minidump_stackwalk": True,
+    "download_symbols": "ondemand",
+
+    "suite_definitions": {
+        "media-tests": {
+            "options": [],
+        },
+        "media-youtube-tests": {
+            "options": [
+                "%(test_manifest)s"
+            ],
+        },
+    },
+}
diff --git a/testing/mozharness/configs/unittests/win_taskcluster_unittest.py b/testing/mozharness/configs/unittests/win_taskcluster_unittest.py
new file mode 100644
index 000000000000..8d3e4278a586
--- /dev/null
+++ b/testing/mozharness/configs/unittests/win_taskcluster_unittest.py
@@ -0,0 +1,282 @@
+import os
+import sys
+
+# OS Specifics
+ABS_WORK_DIR = os.path.join(os.getcwd(), "build")
+BINARY_PATH = os.path.join(ABS_WORK_DIR, "firefox", "firefox.exe")
+INSTALLER_PATH = os.path.join(ABS_WORK_DIR, "installer.zip")
+XPCSHELL_NAME = 'xpcshell.exe'
+EXE_SUFFIX = '.exe'
+DISABLE_SCREEN_SAVER = False
+ADJUST_MOUSE_AND_SCREEN = True
+#####
+config = {
+    "exes": {
+        'python': sys.executable,
+        'virtualenv': [
+            sys.executable,
+            os.path.join(os.path.dirname(sys.executable), 'Lib', 'site-packages', 'virtualenv.py')
+        ],
+        'mozinstall': ['build/venv/scripts/python', 'build/venv/scripts/mozinstall-script.py'],
+        'tooltool.py': [sys.executable, os.path.join(os.environ['MOZILLABUILD'], 'tooltool.py')],
+        'hg': os.path.join(os.environ['PROGRAMFILES'], 'Mercurial', 'hg')
+    },
+    ###
+    "installer_path": INSTALLER_PATH,
+    "binary_path": BINARY_PATH,
+    "xpcshell_name": XPCSHELL_NAME,
+    "virtualenv_path": 'venv',
+    "virtualenv_python_dll": os.path.join(os.path.dirname(sys.executable), "python27.dll"),
+
+    "find_links": [
+        "http://pypi.pvt.build.mozilla.org/pub",
+        "http://pypi.pub.build.mozilla.org/pub",
+    ],
+    "pip_index": False,
+    "exe_suffix": EXE_SUFFIX,
+    "run_file_names": {
+        "mochitest": "runtests.py",
+        "reftest": "runreftest.py",
+        "xpcshell": "runxpcshelltests.py",
+        "cppunittest": "runcppunittests.py",
+        "gtest": "rungtests.py",
+        "jittest": "jit_test.py",
+        "mozbase": "test.py",
+        "mozmill": "runtestlist.py",
+    },
+    "minimum_tests_zip_dirs": [
+        "bin/*",
+        "certs/*",
+        "config/*",
+        "mach",
+        "marionette/*",
+        "modules/*",
+        "mozbase/*",
+        "tools/*",
+    ],
+    "specific_tests_zip_dirs": {
+        "mochitest": ["mochitest/*"],
+        "reftest": ["reftest/*", "jsreftest/*"],
+        "xpcshell": ["xpcshell/*"],
+        "cppunittest": ["cppunittest/*"],
+        "gtest": ["gtest/*"],
+        "jittest": ["jit-test/*"],
+        "mozbase": ["mozbase/*"],
+        "mozmill": ["mozmill/*"],
+    },
+    "suite_definitions": {
+        "cppunittest": {
+            "options": [
+                "--symbols-path=%(symbols_path)s",
+                "--xre-path=%(abs_app_dir)s"
+            ],
+            "run_filename": "runcppunittests.py",
+            "testsdir": "cppunittest"
+        },
+        "jittest": {
+            "options": [
+                "tests/bin/js",
+                "--no-slow",
+                "--no-progress",
+                "--format=automation",
+                "--jitflags=all",
+                "--timeout=970" # Keep in sync with run_timeout below.
+            ],
+            "run_filename": "jit_test.py",
+            "testsdir": "jit-test/jit-test",
+            "run_timeout": 1000 # Keep in sync with --timeout above.
+        },
+        "mochitest": {
+            "options": [
+                "--appname=%(binary_path)s",
+                "--utility-path=tests/bin",
+                "--extra-profile-file=tests/bin/plugins",
+                "--symbols-path=%(symbols_path)s",
+                "--certificate-path=tests/certs",
+                "--quiet",
+                "--log-raw=%(raw_log_file)s",
+                "--log-errorsummary=%(error_summary_file)s",
+                "--screenshot-on-fail",
+                "--cleanup-crashes",
+            ],
+            "run_filename": "runtests.py",
+            "testsdir": "mochitest"
+        },
+        "mozbase": {
+            "options": [
+                "-b",
+                "%(binary_path)s"
+            ],
+            "run_filename": "test.py",
+            "testsdir": "mozbase"
+        },
+        "mozmill": {
+            "options": [
+                "--binary=%(binary_path)s",
+                "--testing-modules-dir=test/modules",
+                "--plugins-path=%(test_plugin_path)s",
+                "--symbols-path=%(symbols_path)s"
+            ],
+            "run_filename": "runtestlist.py",
+            "testsdir": "mozmill"
+        },
+        "reftest": {
+            "options": [
+                "--appname=%(binary_path)s",
+                "--utility-path=tests/bin",
+                "--extra-profile-file=tests/bin/plugins",
+                "--symbols-path=%(symbols_path)s",
+                "--log-raw=%(raw_log_file)s",
+                "--log-errorsummary=%(error_summary_file)s",
+                "--cleanup-crashes",
+            ],
+            "run_filename": "runreftest.py",
+            "testsdir": "reftest"
+        },
+        "xpcshell": {
+            "options": [
+                "--symbols-path=%(symbols_path)s",
+                "--test-plugin-path=%(test_plugin_path)s",
+                "--log-raw=%(raw_log_file)s",
+                "--log-errorsummary=%(error_summary_file)s",
+                "--utility-path=tests/bin",
+            ],
+            "run_filename": "runxpcshelltests.py",
+            "testsdir": "xpcshell"
+        },
+        "gtest": {
+            "options": [
+                "--xre-path=%(abs_res_dir)s",
+                "--cwd=%(gtest_dir)s",
+                "--symbols-path=%(symbols_path)s",
+                "--utility-path=tests/bin",
+                "%(binary_path)s",
+            ],
+            "run_filename": "rungtests.py",
+        },
+    },
+    # local mochi suites
+    "all_mochitest_suites":
+    {
+        "plain": [],
+        "plain-gpu": ["--subsuite=gpu"],
+        "plain-clipboard": ["--subsuite=clipboard"],
+        "plain-chunked": ["--chunk-by-dir=4"],
+        "mochitest-media": ["--subsuite=media"],
+        "chrome": ["--flavor=chrome"],
+        "chrome-gpu": ["--flavor=chrome", "--subsuite=gpu"],
+        "chrome-clipboard": ["--flavor=chrome", "--subsuite=clipboard"],
+        "chrome-chunked": ["--flavor=chrome", "--chunk-by-dir=4"],
+        "browser-chrome": ["--flavor=browser"],
+        "browser-chrome-gpu": ["--flavor=browser", "--subsuite=gpu"],
+        "browser-chrome-clipboard": ["--flavor=browser", "--subsuite=clipboard"],
+        "browser-chrome-chunked": ["--flavor=browser", "--chunk-by-runtime"],
+        "browser-chrome-addons": ["--flavor=browser", "--chunk-by-runtime", "--tag=addons"],
+        "browser-chrome-screenshots": ["--flavor=browser", "--subsuite=screenshots"],
+        "mochitest-gl": ["--subsuite=webgl"],
+        "mochitest-devtools-chrome": ["--flavor=browser", "--subsuite=devtools"],
+        "mochitest-devtools-chrome-chunked": ["--flavor=browser", "--subsuite=devtools", "--chunk-by-runtime"],
+        "mochitest-metro-chrome": ["--flavor=browser", "--metro-immersive"],
+        "jetpack-package": ["--flavor=jetpack-package"],
+        "jetpack-package-clipboard": ["--flavor=jetpack-package", "--subsuite=clipboard"],
+        "jetpack-addon": ["--flavor=jetpack-addon"],
+        "a11y": ["--flavor=a11y"],
+    },
+    # local reftest suites
+    "all_reftest_suites": {
+        "reftest": {
+            'options': ["--suite=reftest"],
+            'tests': ["tests/reftest/tests/layout/reftests/reftest.list"]
+        },
+        "crashtest": {
+            'options': ["--suite=crashtest"],
+            'tests': ["tests/reftest/tests/testing/crashtest/crashtests.list"]
+        },
+        "jsreftest": {
+            'options':["--extra-profile-file=tests/jsreftest/tests/user.js"],
+            'tests': ["tests/jsreftest/tests/jstests.list"]
+        },
+        "reftest-ipc": {
+            'options': ['--suite=reftest',
+                        '--setpref=browser.tabs.remote=true',
+                        '--setpref=browser.tabs.remote.autostart=true',
+                        '--setpref=extensions.e10sBlocksEnabling=false',
+                        '--setpref=layers.async-pan-zoom.enabled=true'],
+            'tests': ['tests/reftest/tests/layout/reftests/reftest-sanity/reftest.list']
+        },
+        "reftest-no-accel": {
+            "options": ["--suite=reftest",
+                        "--setpref=gfx.direct2d.disabled=true",
+                        "--setpref=layers.acceleration.disabled=true"],
+            "tests": ["tests/reftest/tests/layout/reftests/reftest.list"]
+        },
+        "crashtest-ipc": {
+            "options": ["--suite=crashtest",
+                        '--setpref=browser.tabs.remote=true',
+                        '--setpref=browser.tabs.remote.autostart=true',
+                        '--setpref=extensions.e10sBlocksEnabling=false',
+                        '--setpref=layers.async-pan-zoom.enabled=true'],
+            "tests": ['tests/reftest/tests/testing/crashtest/crashtests.list'],
+        },
+    },
+    "all_xpcshell_suites": {
+        "xpcshell": {
+            'options': ["--xpcshell=%(abs_app_dir)s/" + XPCSHELL_NAME,
+                        "--manifest=tests/xpcshell/tests/xpcshell.ini"],
+            'tests': []
+        },
+        "xpcshell-addons": {
+            'options': ["--xpcshell=%(abs_app_dir)s/" + XPCSHELL_NAME,
+                        "--tag=addons",
+                        "--manifest=tests/xpcshell/tests/xpcshell.ini"],
+            'tests': []
+        },
+    },
+    "all_cppunittest_suites": {
+        "cppunittest": ['tests/cppunittest']
+    },
+    "all_gtest_suites": {
+        "gtest": []
+    },
+    "all_jittest_suites": {
+        "jittest": []
+    },
+    "all_mozbase_suites": {
+        "mozbase": []
+    },
+    "run_cmd_checks_enabled": True,
+    "preflight_run_cmd_suites": [
+        {
+            'name': 'disable_screen_saver',
+            'cmd': ['xset', 's', 'off', 's', 'reset'],
+            'architectures': ['32bit', '64bit'],
+            'halt_on_failure': False,
+            'enabled': DISABLE_SCREEN_SAVER
+        },
+        {
+            'name': 'run mouse & screen adjustment script',
+            'cmd': [
+                sys.executable,
+                os.path.join(os.getcwd(),
+                    'mozharness', 'external_tools', 'mouse_and_screen_resolution.py'),
+                '--configuration-file',
+                os.path.join(os.getcwd(),
+                    'mozharness', 'external_tools', 'machine-configuration.json')
+            ],
+            'architectures': ['32bit'],
+            'halt_on_failure': True,
+            'enabled': ADJUST_MOUSE_AND_SCREEN
+        }
+    ],
+    "vcs_output_timeout": 1000,
+    "minidump_save_path": "%(abs_work_dir)s/../minidumps",
+    "buildbot_max_log_size": 52428800,
+    "default_blob_upload_servers": [
+        "https://blobupload.elasticbeanstalk.com",
+    ],
+    "structured_suites": ["reftest"],
+    'blob_uploader_auth_file': 'C:/builds/oauth.txt',
+    "download_minidump_stackwalk": True,
+    "minidump_stackwalk_path": "win32-minidump_stackwalk.exe",
+    "minidump_tooltool_manifest_path": "config/tooltool-manifests/win32/releng.manifest"
+}
diff --git a/testing/mozharness/configs/web_platform_tests/prod_config_windows_taskcluster.py b/testing/mozharness/configs/web_platform_tests/prod_config_windows_taskcluster.py
new file mode 100644
index 000000000000..900b7cff0896
--- /dev/null
+++ b/testing/mozharness/configs/web_platform_tests/prod_config_windows_taskcluster.py
@@ -0,0 +1,48 @@
+# ***** BEGIN LICENSE BLOCK *****
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+# ***** END LICENSE BLOCK *****
+
+# This is a template config file for web-platform-tests test.
+
+import os
+import sys
+
+config = {
+    "options": [
+        "--prefs-root=%(test_path)s/prefs",
+        "--processes=1",
+        "--config=%(test_path)s/wptrunner.ini",
+        "--ca-cert-path=%(test_path)s/certs/cacert.pem",
+        "--host-key-path=%(test_path)s/certs/web-platform.test.key",
+        "--host-cert-path=%(test_path)s/certs/web-platform.test.pem",
+        "--certutil-binary=%(test_install_path)s/bin/certutil",
+    ],
+
+    "exes": {
+        'python': sys.executable,
+        'virtualenv': [
+            sys.executable,
+            os.path.join(os.path.dirname(sys.executable), 'Lib', 'site-packages', 'virtualenv.py')
+        ],
+        'mozinstall': ['build/venv/scripts/python', 'build/venv/scripts/mozinstall-script.py'],
+        'tooltool.py': [sys.executable, os.path.join(os.environ['MOZILLABUILD'], 'tooltool.py')],
+        'hg': os.path.join(os.environ['PROGRAMFILES'], 'Mercurial', 'hg')
+    },
+
+    "find_links": [
+        "http://pypi.pvt.build.mozilla.org/pub",
+        "http://pypi.pub.build.mozilla.org/pub",
+    ],
+
+    "pip_index": False,
+
+    "default_blob_upload_servers": [
+         "https://blobupload.elasticbeanstalk.com",
+    ],
+
+    "blob_uploader_auth_file" : 'C:/builds/oauth.txt',
+
+    "download_minidump_stackwalk": True,
+}
diff --git a/toolkit/components/extensions/ExtensionContent.jsm b/toolkit/components/extensions/ExtensionContent.jsm
index 4cc6d55a51ea..e75c6292244a 100644
--- a/toolkit/components/extensions/ExtensionContent.jsm
+++ b/toolkit/components/extensions/ExtensionContent.jsm
@@ -95,6 +95,7 @@ function Script(extension, options, deferred = PromiseUtils.defer()) {
   this.js = this.options.js || [];
   this.css = this.options.css || [];
   this.remove_css = this.options.remove_css;
+  this.match_about_blank = this.options.match_about_blank;
 
   this.deferred = deferred;
 
@@ -134,6 +135,12 @@ Script.prototype = {
       return false;
     }
 
+    if (this.match_about_blank && ["about:blank", "about:srcdoc"].includes(uri.spec)) {
+      // When matching about:blank/srcdoc documents, the checks below
+      // need to be performed against the "owner" document's URI.
+      uri = window.document.nodePrincipal.URI;
+    }
+
     if (!(this.matches_.matches(uri) || this.matches_host_.matchesIgnoringPath(uri))) {
       return false;
     }
@@ -160,8 +167,6 @@ Script.prototype = {
       return false;
     }
 
-    // TODO: match_about_blank.
-
     return true;
   },
 
@@ -416,11 +421,13 @@ DocumentManager = {
   extensionPageWindows: new Map(),
 
   init() {
+    Services.obs.addObserver(this, "content-document-global-created", false);
     Services.obs.addObserver(this, "document-element-inserted", false);
     Services.obs.addObserver(this, "inner-window-destroyed", false);
   },
 
   uninit() {
+    Services.obs.removeObserver(this, "content-document-global-created");
     Services.obs.removeObserver(this, "document-element-inserted");
     Services.obs.removeObserver(this, "inner-window-destroyed");
   },
@@ -437,13 +444,27 @@ DocumentManager = {
   },
 
   observe: function(subject, topic, data) {
-    if (topic == "document-element-inserted") {
+    // For some types of documents (about:blank), we only see the first
+    // notification, for others (data: URIs) we only observe the second.
+    if (topic == "content-document-global-created" || topic == "document-element-inserted") {
       let document = subject;
       let window = document && document.defaultView;
+
+      if (topic == "content-document-global-created") {
+        window = subject;
+        document = window && window.document;
+      }
+
       if (!document || !document.location || !window) {
         return;
       }
 
+      // Make sure we always load exactly once (notice != used as logical XOR),
+      // usually on document-element-inserted, except for about:blank documents.
+      if ((topic == "content-document-global-created") != (window.location.href == "about:blank")) {
+        return;
+      }
+
       // Make sure we only load into frames that ExtensionContent.init
       // was called on (i.e., not frames for social or sidebars).
       let mm = getWindowMessageManager(window);
@@ -463,7 +484,8 @@ DocumentManager = {
         }
       }
 
-      this.trigger("document_start", window);
+      this.trigger(window);
+
       /* eslint-disable mozilla/balanced-listeners */
       window.addEventListener("DOMContentLoaded", this, true);
       window.addEventListener("load", this, true);
@@ -505,9 +527,9 @@ DocumentManager = {
     // Need to check if we're still on the right page? Greasemonkey does this.
 
     if (event.type == "DOMContentLoaded") {
-      this.trigger("document_end", window);
+      this.trigger(window);
     } else if (event.type == "load") {
-      this.trigger("document_idle", window);
+      this.trigger(window);
     }
   },
 
@@ -643,7 +665,7 @@ DocumentManager = {
     }
   },
 
-  trigger(when, window) {
+  trigger(window) {
     let state = this.getWindowState(window);
 
     if (state == "document_start") {
diff --git a/toolkit/components/extensions/test/mochitest/file_with_about_blank.html b/toolkit/components/extensions/test/mochitest/file_with_about_blank.html
new file mode 100644
index 000000000000..af51c2e52a11
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_with_about_blank.html
@@ -0,0 +1,10 @@
+<!doctype html>
+<html>
+<head>
+  <meta charset="utf-8">
+</head>
+<body>
+  <iframe id="a_b" src="about:blank"></iframe>
+  <iframe srcdoc="galactica actual" src="adama"></iframe>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/mochitest.ini b/toolkit/components/extensions/test/mochitest/mochitest.ini
index aedfba244dd5..a5beee88a998 100644
--- a/toolkit/components/extensions/test/mochitest/mochitest.ini
+++ b/toolkit/components/extensions/test/mochitest/mochitest.ini
@@ -18,6 +18,7 @@ support-files =
   file_WebNavigation_page1.html
   file_WebNavigation_page2.html
   file_WebNavigation_page3.html
+  file_with_about_blank.html
   file_image_good.png
   file_image_bad.png
   file_image_redirect.png
@@ -50,6 +51,7 @@ skip-if = os == 'android' # Android does not currently support windows.
 [test_ext_contentscript_devtools_metadata.html]
 [test_ext_contentscript_exporthelpers.html]
 [test_ext_contentscript_css.html]
+[test_ext_contentscript_about_blank.html]
 [test_ext_contentscript_teardown.html]
 skip-if = (os == 'android') # Android does not support tabs API. Bug 1260250
 [test_ext_exclude_include_globs.html]
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_about_blank.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_about_blank.html
new file mode 100644
index 000000000000..3766678e718d
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_about_blank.html
@@ -0,0 +1,117 @@
+<!doctype html>
+<html>
+<head>
+  <title>Test content script match_about_blank option</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SpawnTask.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(function* test_contentscript_about_blank() {
+  const manifest = {
+    content_scripts: [
+      {
+        match_about_blank: true,
+        matches: ["http://mochi.test/*/file_with_about_blank.html", "http://example.com/*"],
+        all_frames: true,
+        css: ["all.css"],
+        js: ["all.js"],
+      }, {
+        matches: ["http://mochi.test/*/file_with_about_blank.html"],
+        css: ["mochi_without.css"],
+        js: ["mochi_without.js"],
+        all_frames: true,
+      }, {
+        match_about_blank: true,
+        matches: ["http://mochi.test/*/file_with_about_blank.html"],
+        css: ["mochi_with.css"],
+        js: ["mochi_with.js"],
+        all_frames: true,
+      },
+    ],
+  };
+
+  const files = {
+    "all.js": function() {
+      browser.runtime.sendMessage("all");
+    },
+    "all.css": `
+      body { color: red; }
+    `,
+    "mochi_without.js": function() {
+      browser.runtime.sendMessage("mochi_without");
+    },
+    "mochi_without.css": `
+      body { background: yellow; }
+    `,
+    "mochi_with.js": function() {
+      browser.runtime.sendMessage("mochi_with");
+    },
+    "mochi_with.css": `
+      body { text-align: right; }
+    `,
+  };
+
+  function background() {
+    browser.runtime.onMessage.addListener((script, {url}) => {
+      const kind = url.startsWith("about:") ? url : "top";
+      browser.test.sendMessage("script", [script, kind, url]);
+      browser.test.sendMessage(`${script}:${kind}`);
+    });
+  }
+
+  const PATH = "tests/toolkit/components/extensions/test/mochitest/file_with_about_blank.html";
+  const extension = ExtensionTestUtils.loadExtension({manifest, files, background});
+  yield extension.startup();
+
+  let count = 0;
+  extension.onMessage("script", script => {
+    info(`script ran: ${script}`);
+    count++;
+  });
+
+  let win = window.open("http://example.com/" + PATH);
+  yield Promise.all([
+    extension.awaitMessage("all:top"),
+    extension.awaitMessage("all:about:blank"),
+    extension.awaitMessage("all:about:srcdoc"),
+  ]);
+  is(count, 3, "exactly 3 scripts ran");
+  win.close();
+
+  win = window.open("http://mochi.test:8888/" + PATH);
+  yield Promise.all([
+    extension.awaitMessage("all:top"),
+    extension.awaitMessage("all:about:blank"),
+    extension.awaitMessage("all:about:srcdoc"),
+    extension.awaitMessage("mochi_without:top"),
+    extension.awaitMessage("mochi_with:top"),
+    extension.awaitMessage("mochi_with:about:blank"),
+    extension.awaitMessage("mochi_with:about:srcdoc"),
+  ]);
+
+  let style = win.getComputedStyle(win.document.body);
+  is(style.color, "rgb(255, 0, 0)", "top window text color is red");
+  is(style.backgroundColor, "rgb(255, 255, 0)", "top window background is yellow");
+  is(style.textAlign, "right", "top window text is right-aligned");
+
+  let a_b = win.document.getElementById("a_b");
+  style = a_b.contentWindow.getComputedStyle(a_b.contentDocument.body);
+  is(style.color, "rgb(255, 0, 0)", "about:blank iframe text color is red");
+  is(style.backgroundColor, "transparent", "about:blank iframe background is transparent");
+  is(style.textAlign, "right", "about:blank text is right-aligned");
+
+  is(count, 10, "exactly 7 more scripts ran");
+  win.close();
+
+  yield extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/url-classifier/ProtocolParser.cpp b/toolkit/components/url-classifier/ProtocolParser.cpp
index 55060f00c0e5..35a3edea7774 100644
--- a/toolkit/components/url-classifier/ProtocolParser.cpp
+++ b/toolkit/components/url-classifier/ProtocolParser.cpp
@@ -69,6 +69,7 @@ ParseChunkRange(nsACString::const_iterator& aBegin,
 
 ProtocolParser::ProtocolParser()
   : mUpdateStatus(NS_OK)
+  , mUpdateWaitSec(0)
 {
 }
 
@@ -116,7 +117,6 @@ ProtocolParser::GetTableUpdate(const nsACString& aTable)
 
 ProtocolParserV2::ProtocolParserV2()
   : mState(PROTOCOL_STATE_CONTROL)
-  , mUpdateWait(0)
   , mResetRequested(false)
   , mTableUpdate(nullptr)
 {
@@ -180,8 +180,8 @@ ProtocolParserV2::ProcessControl(bool* aDone)
       // Set the table name from the table header line.
       SetCurrentTable(Substring(line, 2));
     } else if (StringBeginsWith(line, NS_LITERAL_CSTRING("n:"))) {
-      if (PR_sscanf(line.get(), "n:%d", &mUpdateWait) != 1) {
-        PARSER_LOG(("Error parsing n: '%s' (%d)", line.get(), mUpdateWait));
+      if (PR_sscanf(line.get(), "n:%d", &mUpdateWaitSec) != 1) {
+        PARSER_LOG(("Error parsing n: '%s' (%d)", line.get(), mUpdateWaitSec));
         return NS_ERROR_FAILURE;
       }
     } else if (line.EqualsLiteral("r:pleasereset")) {
@@ -771,6 +771,10 @@ ProtocolParserProtobuf::End()
     return;
   }
 
+  auto minWaitDuration = response.minimum_wait_duration();
+  mUpdateWaitSec = minWaitDuration.seconds() +
+                   minWaitDuration.nanos() / 1000000000;
+
   for (int i = 0; i < response.list_update_responses_size(); i++) {
     auto r = response.list_update_responses(i);
     nsresult rv = ProcessOneResponse(r);
diff --git a/toolkit/components/url-classifier/ProtocolParser.h b/toolkit/components/url-classifier/ProtocolParser.h
index e2b80375779c..351612cb3076 100644
--- a/toolkit/components/url-classifier/ProtocolParser.h
+++ b/toolkit/components/url-classifier/ProtocolParser.h
@@ -40,6 +40,8 @@ public:
   nsresult Begin();
   virtual nsresult AppendStream(const nsACString& aData) = 0;
 
+  uint32_t UpdateWaitSec() { return mUpdateWaitSec; }
+
   // Notify that the inbound data is ready for parsing if progressive
   // parsing is not supported, for example in V4.
   virtual void End() = 0;
@@ -52,10 +54,9 @@ public:
 
   // These are only meaningful to V2. Since they were originally public,
   // moving them to ProtocolParserV2 requires a dymamic cast in the call
-  // sites. As a result, we will leave them until we remove support 
+  // sites. As a result, we will leave them until we remove support
   // for V2 entirely..
   virtual const nsTArray<ForwardedUpdate> &Forwards() const { return mForwards; }
-  virtual int32_t UpdateWait() { return 0; }
   virtual bool ResetRequested() { return false; }
 
 protected:
@@ -73,6 +74,9 @@ protected:
   // The table names that were requested from the client.
   nsTArray<nsCString> mRequestedTables;
 
+  // How long we should wait until the next update.
+  uint32_t mUpdateWaitSec;
+
 private:
   void CleanupUpdates();
 };
@@ -91,7 +95,6 @@ public:
 
   // Update information.
   virtual const nsTArray<ForwardedUpdate> &Forwards() const override { return mForwards; }
-  virtual int32_t UpdateWait() override { return mUpdateWait; }
   virtual bool ResetRequested() override { return mResetRequested; }
 
 private:
@@ -147,7 +150,6 @@ private:
   };
   ChunkState mChunkState;
 
-  uint32_t mUpdateWait;
   bool mResetRequested;
 
   // Updates to apply to the current table being parsed.
diff --git a/toolkit/components/url-classifier/content/listmanager.js b/toolkit/components/url-classifier/content/listmanager.js
index d55d03c6e2f8..68325bec8fca 100644
--- a/toolkit/components/url-classifier/content/listmanager.js
+++ b/toolkit/components/url-classifier/content/listmanager.js
@@ -204,7 +204,7 @@ PROT_ListManager.prototype.kickoffUpdate_ = function (onDiskTableData)
   for (var updateUrl in this.needsUpdate_) {
     // If we haven't already kicked off updates for this updateUrl, set a
     // non-repeating timer for it. The timer delay will be reset either on
-    // updateSuccess to this.updateinterval, or backed off on downloadError.
+    // updateSuccess to this.updateInterval, or backed off on downloadError.
     // Don't set the updateChecker unless at least one table has updates
     // enabled.
     if (this.updatesNeeded_(updateUrl) && !this.updateCheckers_[updateUrl]) {
@@ -492,12 +492,15 @@ PROT_ListManager.prototype.makeUpdateRequestForEntry_ = function(updateUrl,
  *        wait before requesting again.
  */
 PROT_ListManager.prototype.updateSuccess_ = function(tableList, updateUrl,
-                                                     waitForUpdate) {
+                                                     waitForUpdateSec) {
   log("update success for " + tableList + " from " + updateUrl + ": " +
-      waitForUpdate + "\n");
+      waitForUpdateSec + "\n");
+
+  // The time unit below are all milliseconds if not specified.
+
   var delay = 0;
-  if (waitForUpdate) {
-    delay = parseInt(waitForUpdate, 10) * 1000;
+  if (waitForUpdateSec) {
+    delay = parseInt(waitForUpdateSec, 10) * 1000;
   }
   // As long as the delay is something sane (5 min to 1 day), update
   // our delay time for requesting updates. We always use a non-repeating
@@ -556,7 +559,7 @@ PROT_ListManager.prototype.updateSuccess_ = function(tableList, updateUrl,
 PROT_ListManager.prototype.updateError_ = function(table, updateUrl, result) {
   log("update error for " + table + " from " + updateUrl + ": " + result + "\n");
   // There was some trouble applying the updates. Don't try again for at least
-  // updateInterval seconds.
+  // updateInterval milliseconds.
   this.updateCheckers_[updateUrl] =
     new G_Alarm(BindToObject(this.checkForUpdates, this, updateUrl),
                 this.updateInterval, false);
diff --git a/toolkit/components/url-classifier/nsUrlClassifierDBService.cpp b/toolkit/components/url-classifier/nsUrlClassifierDBService.cpp
index c74861b7bab7..50afd4369d1d 100644
--- a/toolkit/components/url-classifier/nsUrlClassifierDBService.cpp
+++ b/toolkit/components/url-classifier/nsUrlClassifierDBService.cpp
@@ -392,7 +392,7 @@ void
 nsUrlClassifierDBServiceWorker::ResetUpdate()
 {
   LOG(("ResetUpdate"));
-  mUpdateWait = 0;
+  mUpdateWaitSec = 0;
   mUpdateStatus = NS_OK;
   mUpdateObserver = nullptr;
 }
@@ -543,8 +543,8 @@ nsUrlClassifierDBServiceWorker::FinishStream()
   mProtocolParser->End();
 
   if (NS_SUCCEEDED(mProtocolParser->Status())) {
-    if (mProtocolParser->UpdateWait()) {
-      mUpdateWait = mProtocolParser->UpdateWait();
+    if (mProtocolParser->UpdateWaitSec()) {
+      mUpdateWaitSec = mProtocolParser->UpdateWaitSec();
     }
     // XXX: Only allow forwards from the initial update?
     const nsTArray<ProtocolParser::ForwardedUpdate> &forwards =
@@ -592,8 +592,8 @@ nsUrlClassifierDBServiceWorker::FinishUpdate()
   mMissCache.Clear();
 
   if (NS_SUCCEEDED(mUpdateStatus)) {
-    LOG(("Notifying success: %d", mUpdateWait));
-    mUpdateObserver->UpdateSuccess(mUpdateWait);
+    LOG(("Notifying success: %d", mUpdateWaitSec));
+    mUpdateObserver->UpdateSuccess(mUpdateWaitSec);
   } else if (NS_ERROR_NOT_IMPLEMENTED == mUpdateStatus) {
     LOG(("Treating NS_ERROR_NOT_IMPLEMENTED a successful update "
          "but still mark it spoiled."));
diff --git a/toolkit/components/url-classifier/nsUrlClassifierDBService.h b/toolkit/components/url-classifier/nsUrlClassifierDBService.h
index 23288d659404..867141162e0e 100644
--- a/toolkit/components/url-classifier/nsUrlClassifierDBService.h
+++ b/toolkit/components/url-classifier/nsUrlClassifierDBService.h
@@ -217,7 +217,7 @@ private:
   // storing a series of updates.
   nsTArray<mozilla::safebrowsing::TableUpdate*> mTableUpdates;
 
-  int32_t mUpdateWait;
+  uint32_t mUpdateWaitSec;
 
   // Entries that cannot be completed. We expect them to die at
   // the next update
diff --git a/toolkit/components/url-classifier/tests/gtest/TestProtocolParser.cpp b/toolkit/components/url-classifier/tests/gtest/TestProtocolParser.cpp
new file mode 100644
index 000000000000..543588fa1da2
--- /dev/null
+++ b/toolkit/components/url-classifier/tests/gtest/TestProtocolParser.cpp
@@ -0,0 +1,87 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+#include "gtest/gtest.h"
+#include "ProtocolParser.h"
+#include "mozilla/EndianUtils.h"
+
+using namespace mozilla;
+using namespace mozilla::safebrowsing;
+
+typedef FetchThreatListUpdatesResponse_ListUpdateResponse ListUpdateResponse;
+
+static void
+InitUpdateResponse(ListUpdateResponse* aUpdateResponse,
+                   ThreatType aThreatType,
+                   const nsACString& aState,
+                   const nsACString& aChecksum,
+                   bool isFullUpdate,
+                   const nsTArray<uint32_t>& aFixedLengthPrefixes);
+
+static void
+DumpBinary(const nsACString& aBinary);
+
+TEST(ProtocolParser, UpdateWait)
+{
+  // Top level response which contains a list of update response
+  // for different lists.
+  FetchThreatListUpdatesResponse response;
+
+  auto r = response.mutable_list_update_responses()->Add();
+  InitUpdateResponse(r, SOCIAL_ENGINEERING_PUBLIC,
+                        nsCString("sta\x00te", 6),
+                        nsCString("check\x0sum", 9),
+                        true,
+                        {0, 1, 2, 3});
+
+  // Set min wait duration.
+  auto minWaitDuration = response.mutable_minimum_wait_duration();
+  minWaitDuration->set_seconds(8);
+  minWaitDuration->set_nanos(1 * 1000000000);
+
+  std::string s;
+  response.SerializeToString(&s);
+
+  DumpBinary(nsCString(s.c_str(), s.length()));
+
+  ProtocolParser* p = new ProtocolParserProtobuf();
+  p->AppendStream(nsCString(s.c_str(), s.length()));
+  p->End();
+  ASSERT_EQ(p->UpdateWaitSec(), 9u);
+  delete p;
+}
+
+static void
+InitUpdateResponse(ListUpdateResponse* aUpdateResponse,
+                   ThreatType aThreatType,
+                   const nsACString& aState,
+                   const nsACString& aChecksum,
+                   bool isFullUpdate,
+                   const nsTArray<uint32_t>& aFixedLengthPrefixes)
+{
+  aUpdateResponse->set_threat_type(aThreatType);
+  aUpdateResponse->set_new_client_state(aState.BeginReading(), aState.Length());
+  aUpdateResponse->mutable_checksum()->set_sha256(aChecksum.BeginReading(), aChecksum.Length());
+  aUpdateResponse->set_response_type(isFullUpdate ? ListUpdateResponse::FULL_UPDATE
+                                                  : ListUpdateResponse::PARTIAL_UPDATE);
+
+  auto additions = aUpdateResponse->mutable_additions()->Add();
+  additions->set_compression_type(RAW);
+  auto rawHashes = additions->mutable_raw_hashes();
+  rawHashes->set_prefix_size(4);
+  auto prefixes = rawHashes->mutable_raw_hashes();
+  for (auto p : aFixedLengthPrefixes) {
+    char buffer[4];
+    NativeEndian::copyAndSwapToBigEndian(buffer, &p, 1);
+    prefixes->append(buffer, 4);
+  }
+}
+
+static void DumpBinary(const nsACString& aBinary)
+{
+  nsCString s;
+  for (size_t i = 0; i < aBinary.Length(); i++) {
+    s.AppendPrintf("\\x%.2X", (uint8_t)aBinary[i]);
+  }
+  printf("%s\n", s.get());
+}
\ No newline at end of file
diff --git a/toolkit/components/url-classifier/tests/gtest/moz.build b/toolkit/components/url-classifier/tests/gtest/moz.build
index fb641d70a613..68fdf7846073 100644
--- a/toolkit/components/url-classifier/tests/gtest/moz.build
+++ b/toolkit/components/url-classifier/tests/gtest/moz.build
@@ -11,6 +11,7 @@ LOCAL_INCLUDES += [
 UNIFIED_SOURCES += [
     'TestChunkSet.cpp',
     'TestPerProviderDirectory.cpp',
+    'TestProtocolParser.cpp',
     'TestRiceDeltaDecoder.cpp',
     'TestSafebrowsingHash.cpp',
     'TestSafeBrowsingProtobuf.cpp',
diff --git a/xpcom/base/nscore.h b/xpcom/base/nscore.h
index 14c12cdddd09..f6e73c6bc70c 100644
--- a/xpcom/base/nscore.h
+++ b/xpcom/base/nscore.h
@@ -159,16 +159,6 @@
 # define MOZ_DEPRECATED
 #endif
 
-/**
- * Printf style formats
- */
-#ifdef __GNUC__
-#define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck)  \
-    __attribute__ ((format (printf, stringIndex, firstToCheck)))
-#else
-#define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck)
-#endif
-
 /**
  * Generic API modifiers which return the standard XPCOM nsresult type
  *