Bug 1262731 - Add JS_InitWithFailureDiagnostic(). r=sfink.

This will help identify the cause of some Firefox start-up crashes when JS
initialization fails.

--HG--
extra : rebase_source : 3ed3c5e60f487e0ca11dc13bab93aa820ca8273f

js/public/Initialization.h

@@ -61,6 +61,14 @@ JS_SetICUMemoryFunctions(JS_ICUAllocFn allocFn,
 extern JS_PUBLIC_API(bool)
 JS_Init(void);
 
+/**
+ * A variant of JS_Init. On success it returns nullptr. On failure it returns a
+ * pointer to a string literal that describes how initialization failed, which
+ * can be useful for debugging purposes.
+ */
+extern JS_PUBLIC_API(const char*)
+JS_InitWithFailureDiagnostic(void);
+
 /**
  * Destroy free-standing resources allocated by SpiderMonkey, not associated
  * with any runtime, context, or other structure.

js/src/vm/DateTime.h

@@ -119,7 +119,7 @@ class DateTimeInfo
         }
     };
 
-    friend bool ::JS_Init();
+    friend const char* ::JS_InitWithFailureDiagnostic();
 
     // Initialize global date/time tracking state.  This operation occurs
     // during, and is restricted to, SpiderMonkey initialization.

js/src/vm/Initialization.cpp

@@ -59,8 +59,8 @@ CheckMessageParameterCounts()
 }
 #endif /* DEBUG */
 
-JS_PUBLIC_API(bool)
-JS_Init(void)
+JS_PUBLIC_API(const char*)
+JS_InitWithFailureDiagnostic(void)
 {
     MOZ_ASSERT(libraryInitState == InitState::Uninitialized,
                "must call JS_Init once before any JSAPI operation except "
@@ -76,18 +76,18 @@ JS_Init(void)
 
     using js::TlsPerThreadData;
     if (!TlsPerThreadData.init())
-        return false;
+        return "JS_InitWithFailureDiagnostic: TlsPerThreadData.init() failed";
 
 #if defined(DEBUG) || defined(JS_OOM_BREAKPOINT)
     if (!js::oom::InitThreadType())
-        return false;
+        return "JS_InitWithFailureDiagnostic: js::oom::InitThreadType() failed";
     js::oom::SetThreadType(js::oom::THREAD_TYPE_MAIN);
 #endif
 
     js::jit::ExecutableAllocator::initStatic();
 
     if (!js::jit::InitializeIon())
-        return false;
+        return "JS_InitWithFailureDiagnostic: js::jit::InitializeIon() failed";
 
     js::DateTimeInfo::init();
 
@@ -95,20 +95,27 @@ JS_Init(void)
     UErrorCode err = U_ZERO_ERROR;
     u_init(&err);
     if (U_FAILURE(err))
-        return false;
+        return "JS_InitWithFailureDiagnostic: u_init() failed";
 #endif // EXPOSE_INTL_API
 
     if (!js::CreateHelperThreadsState())
-        return false;
+        return "JS_InitWithFailureDiagnostic: js::CreateHelperThreadState() failed";
 
     if (!FutexRuntime::initialize())
-        return false;
+        return "JS_InitWithFailureDiagnostic: FutexRuntime::initialize() failed";
 
     if (!js::gcstats::Statistics::initialize())
-        return false;
+        return "JS_InitWithFailureDiagnostic: js::gcstats::Statistics::initialize() failed";
 
     libraryInitState = InitState::Running;
-    return true;
+    return nullptr;
+}
+
+JS_PUBLIC_API(bool)
+JS_Init(void)
+{
+    const char* failure = JS_InitWithFailureDiagnostic();
+    return !failure;
 }
 
 JS_PUBLIC_API(void)

xpcom/build/XPCOMInit.cpp

@@ -704,8 +704,9 @@ NS_InitXPCOM2(nsIServiceManager** aResult,
 #endif
 
   // Initialize the JS engine.
-  if (!JS_Init()) {
-    NS_RUNTIMEABORT("JS_Init failed");
+  const char* jsInitFailureReason = JS_InitWithFailureDiagnostic();
+  if (jsInitFailureReason) {
+    NS_RUNTIMEABORT(jsInitFailureReason);
   }
 
   rv = nsComponentManagerImpl::gComponentManager->Init();