Bug 1265030 - Show symbolic nsresult name in NS_ENSURE_SUCCESS warning. r=mccr8

Through their use of Smprintf, the existing warning message formatting
is resistant to OOM errors.  So I figured that we should probably use
something that doesn't infallibly allocate like GetErrorName does.

Differential Revision: https://phabricator.services.mozilla.com/D70771

--HG--
extra : moz-landing-system : lando

xpcom/base/ErrorNames.cpp

@@ -14,6 +14,8 @@
 
 namespace mozilla {
 
+const char* GetStaticErrorName(nsresult rv) { return GetErrorNameInternal(rv); }
+
 void GetErrorName(nsresult rv, nsACString& name) {
   if (const char* errorName = GetErrorNameInternal(rv)) {
     name.AssignASCII(errorName);

xpcom/base/ErrorNames.h

@@ -19,6 +19,11 @@ namespace mozilla {
 // "NS_ERROR_GENERATE_FAILURE(<module>, <code>)".
 void GetErrorName(nsresult rv, nsACString& name);
 
+// Same as GetErrorName, except that only nsresult values with statically
+// known symbolic names are handled. For all other values, nullptr is
+// returned.
+const char* GetStaticErrorName(nsresult rv);
+
 }  // namespace mozilla
 
 #endif  // mozilla_ErrorNames_h

xpcom/base/nsDebug.h

@@ -17,6 +17,7 @@
 #include <stdarg.h>
 
 #ifdef DEBUG
+#  include "mozilla/ErrorNames.h"
 #  include "mozilla/IntegerPrintfMacros.h"
 #  include "mozilla/Printf.h"
 #endif
@@ -247,18 +248,22 @@ inline void MOZ_PretendNoReturn() MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS {}
 
 #if defined(DEBUG) && !defined(XPCOM_GLUE_AVOID_NSPR)
 
-#  define NS_ENSURE_SUCCESS_BODY(res, ret)            \
-    mozilla::SmprintfPointer msg = mozilla::Smprintf( \
-        "NS_ENSURE_SUCCESS(%s, %s) failed with "      \
-        "result 0x%" PRIX32,                          \
-        #res, #ret, static_cast<uint32_t>(__rv));     \
+#  define NS_ENSURE_SUCCESS_BODY(res, ret)                         \
+    const char* name = mozilla::GetStaticErrorName(__rv);          \
+    mozilla::SmprintfPointer msg = mozilla::Smprintf(              \
+        "NS_ENSURE_SUCCESS(%s, %s) failed with "                   \
+        "result 0x%" PRIX32 "%s%s%s",                              \
+        #res, #ret, static_cast<uint32_t>(__rv), name ? " (" : "", \
+        name ? name : "", name ? ")" : "");                        \
     NS_WARNING(msg.get());
 
-#  define NS_ENSURE_SUCCESS_BODY_VOID(res)            \
-    mozilla::SmprintfPointer msg = mozilla::Smprintf( \
-        "NS_ENSURE_SUCCESS_VOID(%s) failed with "     \
-        "result 0x%" PRIX32,                          \
-        #res, static_cast<uint32_t>(__rv));           \
+#  define NS_ENSURE_SUCCESS_BODY_VOID(res)                                     \
+    const char* name = mozilla::GetStaticErrorName(__rv);                      \
+    mozilla::SmprintfPointer msg = mozilla::Smprintf(                          \
+        "NS_ENSURE_SUCCESS_VOID(%s) failed with "                              \
+        "result 0x%" PRIX32 "%s%s%s",                                          \
+        #res, static_cast<uint32_t>(__rv), name ? " (" : "", name ? name : "", \
+        name ? ")" : "");                                                      \
     NS_WARNING(msg.get());
 
 #else