Bug 1257919 part 4. Stop returning StackFrame instances from exceptions::CreateStack. C++ callers of GetCurrentJSStack or exceptions::CreateStack always check for null anyway, and none of them seem to want this non-JS thing. r=khuey

dom/base/Console.cpp

@@ -1034,8 +1034,7 @@ Console::NoopMethod()
 static
 nsresult
 StackFrameToStackEntry(nsIStackFrame* aStackFrame,
-                       ConsoleStackEntry& aStackEntry,
-                       uint32_t aLanguage)
+                       ConsoleStackEntry& aStackEntry)
 {
   MOZ_ASSERT(aStackFrame);
 
@@ -1064,7 +1063,7 @@ StackFrameToStackEntry(nsIStackFrame* aStackFrame,
     aStackEntry.mAsyncCause.Construct(cause);
   }
 
-  aStackEntry.mLanguage = aLanguage;
+  aStackEntry.mLanguage = nsIProgrammingLanguage::JAVASCRIPT;
   return NS_OK;
 }
 
@@ -1075,16 +1074,10 @@ ReifyStack(nsIStackFrame* aStack, nsTArray<ConsoleStackEntry>& aRefiedStack)
   nsCOMPtr<nsIStackFrame> stack(aStack);
 
   while (stack) {
-    uint32_t language;
-    nsresult rv = stack->GetLanguage(&language);
+    ConsoleStackEntry& data = *aRefiedStack.AppendElement();
+    nsresult rv = StackFrameToStackEntry(stack, data);
     NS_ENSURE_SUCCESS(rv, rv);
 
-    if (language == nsIProgrammingLanguage::JAVASCRIPT) {
-      ConsoleStackEntry& data = *aRefiedStack.AppendElement();
-      rv = StackFrameToStackEntry(stack, data, language);
-      NS_ENSURE_SUCCESS(rv, rv);
-    }
-
     nsCOMPtr<nsIStackFrame> caller;
     rv = stack->GetCaller(getter_AddRefs(caller));
     NS_ENSURE_SUCCESS(rv, rv);
@@ -1129,39 +1122,15 @@ Console::Method(JSContext* aCx, MethodName aMethodName,
                       DEFAULT_MAX_STACKTRACE_DEPTH : 1;
   nsCOMPtr<nsIStackFrame> stack = CreateStack(aCx, maxDepth);
 
-  if (!stack) {
-    return;
+  if (stack) {
+    callData->mTopStackFrame.emplace();
+    nsresult rv = StackFrameToStackEntry(stack,
+                                         *callData->mTopStackFrame);
+    if (NS_FAILED(rv)) {
+      return;
+    }
   }
 
-  // Walk up to the first JS stack frame and save it if we find it.
-  do {
-    uint32_t language;
-    nsresult rv = stack->GetLanguage(&language);
-    if (NS_FAILED(rv)) {
-      return;
-    }
-
-    if (language == nsIProgrammingLanguage::JAVASCRIPT) {
-      callData->mTopStackFrame.emplace();
-      nsresult rv = StackFrameToStackEntry(stack,
-                                           *callData->mTopStackFrame,
-                                           language);
-      if (NS_FAILED(rv)) {
-        return;
-      }
-
-      break;
-    }
-
-    nsCOMPtr<nsIStackFrame> caller;
-    rv = stack->GetCaller(getter_AddRefs(caller));
-    if (NS_FAILED(rv)) {
-      return;
-    }
-
-    stack.swap(caller);
-  } while (stack);
-
   if (NS_IsMainThread()) {
     callData->mStack = stack;
   } else {

dom/base/DOMException.cpp

@@ -218,37 +218,7 @@ Exception::Exception(const nsACString& aMessage,
     sEverMadeOneFromFactory = true;
   }
 
-  nsCOMPtr<nsIStackFrame> location;
-  if (aLocation) {
-    location = aLocation;
-  } else {
-    location = GetCurrentJSStack();
-    // it is legal for there to be no active JS stack, if C++ code
-    // is operating on a JS-implemented interface pointer without
-    // having been called in turn by JS.  This happens in the JS
-    // component loader, and will become more common as additional
-    // components are implemented in JS.
-  }
-  // We want to trim off any leading native 'dataless' frames
-  if (location) {
-    while (1) {
-      uint32_t language;
-      int32_t lineNumber;
-      if (NS_FAILED(location->GetLanguage(&language)) ||
-          language == nsIProgrammingLanguage::JAVASCRIPT ||
-          NS_FAILED(location->GetLineNumber(&lineNumber)) ||
-          lineNumber) {
-        break;
-      }
-      nsCOMPtr<nsIStackFrame> caller;
-      if (NS_FAILED(location->GetCaller(getter_AddRefs(caller))) || !caller) {
-        break;
-      }
-      location = caller;
-    }
-  }
-
-  Initialize(aMessage, aResult, aName, location, aData);
+  Initialize(aMessage, aResult, aName, aLocation, aData);
 }
 
 Exception::Exception()
@@ -454,12 +424,11 @@ Exception::Initialize(const nsACString& aMessage, nsresult aResult,
   if (aLocation) {
     mLocation = aLocation;
   } else {
-    nsresult rv;
-    nsXPConnect* xpc = nsXPConnect::XPConnect();
-    rv = xpc->GetCurrentJSStack(getter_AddRefs(mLocation));
-    if (NS_FAILED(rv)) {
-      return rv;
-    }
+    mLocation = GetCurrentJSStack();
+    // it is legal for there to be no active JS stack, if C++ code
+    // is operating on a JS-implemented interface pointer without
+    // having been called in turn by JS.  This happens in the JS
+    // component loader.
   }
 
   mData = aData;

dom/base/nsHostObjectProtocolHandler.cpp

@@ -7,6 +7,7 @@
 #include "nsHostObjectProtocolHandler.h"
 
 #include "DOMMediaStream.h"
+#include "mozilla/dom/Exceptions.h"
 #include "mozilla/dom/File.h"
 #include "mozilla/dom/MediaSource.h"
 #include "mozilla/LoadInfo.h"
@@ -201,11 +202,7 @@ class BlobURLsReporter final : public nsIMemoryReporter
       return;
     }
 
-    nsresult rv;
-    nsIXPConnect* xpc = nsContentUtils::XPConnect();
-    nsCOMPtr<nsIStackFrame> frame;
-    rv = xpc->GetCurrentJSStack(getter_AddRefs(frame));
-    NS_ENSURE_SUCCESS_VOID(rv);
+    nsCOMPtr<nsIStackFrame> frame = dom::GetCurrentJSStack(maxFrames);
 
     nsAutoCString origin;
     nsCOMPtr<nsIURI> principalURI;
@@ -214,7 +211,7 @@ class BlobURLsReporter final : public nsIMemoryReporter
       principalURI->GetPrePath(origin);
     }
 
-    for (uint32_t i = 0; i < maxFrames && frame; ++i) {
+    for (uint32_t i = 0; frame; ++i) {
       nsString fileNameUTF16;
       int32_t lineNumber = 0;
 
@@ -246,8 +243,10 @@ class BlobURLsReporter final : public nsIMemoryReporter
         stack += ")/";
       }
 
-      rv = frame->GetCaller(getter_AddRefs(frame));
+      nsCOMPtr<nsIStackFrame> caller;
+      nsresult rv = frame->GetCaller(getter_AddRefs(caller));
       NS_ENSURE_SUCCESS_VOID(rv);
+      caller.swap(frame);
     }
   }
 

dom/bindings/Exceptions.cpp

@@ -175,7 +175,7 @@ CreateException(JSContext* aCx, nsresult aRv, const nsACString& aMessage)
 }
 
 already_AddRefed<nsIStackFrame>
-GetCurrentJSStack()
+GetCurrentJSStack(int32_t aMaxDepth)
 {
   // is there a current context available?
   JSContext* cx = nullptr;
@@ -191,13 +191,7 @@ GetCurrentJSStack()
     return nullptr;
   }
 
-  nsCOMPtr<nsIStackFrame> stack = exceptions::CreateStack(cx);
-  if (!stack) {
-    return nullptr;
-  }
-
-  // Note that CreateStack only returns JS frames, so we're done here.
-  return stack.forget();
+  return exceptions::CreateStack(cx, aMaxDepth);
 }
 
 AutoForceSetExceptionOnContext::AutoForceSetExceptionOnContext(JSContext* aCx)
@@ -795,8 +789,8 @@ NS_IMETHODIMP StackFrame::ToString(JSContext* aCx, nsACString& _retval)
   return NS_OK;
 }
 
-/* static */ already_AddRefed<nsIStackFrame>
-JSStackFrame::CreateStack(JSContext* aCx, int32_t aMaxDepth)
+already_AddRefed<nsIStackFrame>
+CreateStack(JSContext* aCx, int32_t aMaxDepth)
 {
   static const unsigned MAX_FRAMES = 100;
   if (aMaxDepth < 0) {
@@ -808,19 +802,12 @@ JSStackFrame::CreateStack(JSContext* aCx, int32_t aMaxDepth)
     return nullptr;
   }
 
-  nsCOMPtr<nsIStackFrame> first;
   if (!stack) {
-    first = new StackFrame();
-  } else {
-    first = new JSStackFrame(stack);
+    return nullptr;
   }
-  return first.forget();
-}
 
-already_AddRefed<nsIStackFrame>
-CreateStack(JSContext* aCx, int32_t aMaxDepth)
-{
-  return JSStackFrame::CreateStack(aCx, aMaxDepth);
+  nsCOMPtr<nsIStackFrame> frame = new JSStackFrame(stack);
+  return frame.forget();
 }
 
 } // namespace exceptions

dom/bindings/Exceptions.h

@@ -48,8 +48,11 @@ already_AddRefed<Exception>
 CreateException(JSContext* aCx, nsresult aRv,
                 const nsACString& aMessage = EmptyCString());
 
+// aMaxDepth can be used to define a maximal depth for the stack trace. If the
+// value is -1, a default maximal depth will be selected.  Will return null if
+// there is no JS stack right now.
 already_AddRefed<nsIStackFrame>
-GetCurrentJSStack();
+GetCurrentJSStack(int32_t aMaxDepth = -1);
 
 // Throwing a TypeError on an ErrorResult may result in SpiderMonkey using its
 // own error reporting mechanism instead of just setting the exception on the
@@ -68,7 +71,8 @@ public:
 namespace exceptions {
 
 // aMaxDepth can be used to define a maximal depth for the stack trace. If the
-// value is -1, a default maximal depth will be selected.
+// value is -1, a default maximal depth will be selected.  Will return null if
+// there is no JS stack right now.
 already_AddRefed<nsIStackFrame>
 CreateStack(JSContext* aCx, int32_t aMaxDepth = -1);
 

js/xpconnect/idl/nsIXPConnect.idl

@@ -412,6 +412,7 @@ interface nsIXPConnect : nsISupports
     [noscript,notxpcom,nostdcall] JSContextPtr getCurrentJSContext();
     [noscript,notxpcom,nostdcall] JSContextPtr getSafeJSContext();
 
+    // Will return null if there is no JS stack right now.
     readonly attribute nsIStackFrame                CurrentJSStack;
     readonly attribute nsAXPCNativeCallContextPtr   CurrentNativeCallContext;
 

js/xpconnect/idl/xpccomponents.idl

@@ -710,6 +710,7 @@ interface nsIXPCComponents : nsIXPCComponentsBase
 {
     readonly attribute nsIXPCComponents_Classes         classes;
     readonly attribute nsIXPCComponents_ClassesByID     classesByID;
+    // Will return null if there is no JS stack right now.
     readonly attribute nsIStackFrame                    stack;
     readonly attribute nsIComponentManager              manager;
     readonly attribute nsIXPCComponents_Utils           utils;