From c93fca087ecd15439c21232c68c8ff6164023197 Mon Sep 17 00:00:00 2001
From: Michael Layzell <michael@thelayzells.com>
Date: Tue, 11 Jul 2017 16:52:09 -0400
Subject: [PATCH] Bug 1380096 - Don't require that sMainThreadRunnableName is
 null-terminated, r=erahm

MozReview-Commit-ID: 9Zo1vjmKzZC
---
 xpcom/threads/ThreadStackHelper.cpp | 13 +++++++------
 xpcom/threads/nsThread.cpp          |  8 +++++---
 xpcom/threads/nsThread.h            |  2 +-
 3 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/xpcom/threads/ThreadStackHelper.cpp b/xpcom/threads/ThreadStackHelper.cpp
index cf4e7843ef59..933dafb5bb84 100644
--- a/xpcom/threads/ThreadStackHelper.cpp
+++ b/xpcom/threads/ThreadStackHelper.cpp
@@ -138,7 +138,7 @@ ThreadStackHelper::GetStacksInternal(Stack* aStack,
   ScopedSetPtr<NativeStack> nativeStackPtr(mNativeStackToFill, aNativeStack);
 #endif
 
-  char nameBuffer[1000] = {0};
+  Vector<char, 1000> nameBuffer;
   auto callback = [&, this] (void** aPCs, size_t aCount, bool aIsMainThread) {
     // NOTE: We cannot allocate any memory in this callback, as the target
     // thread is suspended, so we first copy it into a stack-allocated buffer,
@@ -149,9 +149,10 @@ ThreadStackHelper::GetStacksInternal(Stack* aStack,
     // main thread, so we only want to read sMainThreadRunnableName and copy its
     // value in the case that we are currently suspending the main thread.
     if (aIsMainThread && nsThread::sMainThreadRunnableName) {
-      strncpy(nameBuffer, nsThread::sMainThreadRunnableName, sizeof(nameBuffer));
-      // Make sure the string is null-terminated.
-      nameBuffer[sizeof(nameBuffer) - 1] = '\0';
+      MOZ_ALWAYS_TRUE(
+        nameBuffer.append(nsThread::sMainThreadRunnableName->BeginReading(),
+                          std::min(uint32_t(nameBuffer.sMaxInlineStorage),
+                                   uint32_t(nsThread::sMainThreadRunnableName->Length()))));
     }
 
 #ifdef MOZ_THREADSTACKHELPER_PSEUDO
@@ -177,8 +178,8 @@ ThreadStackHelper::GetStacksInternal(Stack* aStack,
   }
 
   // Copy the name buffer allocation into the output string.
-  if (nameBuffer[0] != 0) {
-    aRunnableName = nameBuffer;
+  if (nameBuffer.length() > 0) {
+    aRunnableName.AssignASCII(nameBuffer.begin(), nameBuffer.length());
   }
 #endif
 }
diff --git a/xpcom/threads/nsThread.cpp b/xpcom/threads/nsThread.cpp
index 202025c5ca35..cb74b9a62299 100644
--- a/xpcom/threads/nsThread.cpp
+++ b/xpcom/threads/nsThread.cpp
@@ -99,7 +99,7 @@ static LazyLogModule sThreadLog("nsThread");
 
 NS_DECL_CI_INTERFACE_GETTER(nsThread)
 
-const char* nsThread::sMainThreadRunnableName = nullptr;
+const nsACString* nsThread::sMainThreadRunnableName = nullptr;
 
 //-----------------------------------------------------------------------------
 // Because we do not have our own nsIFactory, we have to implement nsIClassInfo
@@ -1422,15 +1422,17 @@ nsThread::ProcessNextEvent(bool aMayWait, bool* aResult)
 
       // If we're on the main thread, we want to record our current runnable's
       // name in a static so that BHR can record it.
-      const char* restoreRunnableName = nullptr;
+      const nsACString* restoreRunnableName = nullptr;
       auto clear = MakeScopeExit([&] {
         if (MAIN_THREAD == mIsMainThread) {
+          MOZ_ASSERT(NS_IsMainThread());
           sMainThreadRunnableName = restoreRunnableName;
         }
       });
       if (MAIN_THREAD == mIsMainThread) {
+        MOZ_ASSERT(NS_IsMainThread());
         restoreRunnableName = sMainThreadRunnableName;
-        sMainThreadRunnableName = name.get();
+        sMainThreadRunnableName = &name;
       }
 #endif
 
diff --git a/xpcom/threads/nsThread.h b/xpcom/threads/nsThread.h
index 5bbe8d8d78a7..87ce954960b5 100644
--- a/xpcom/threads/nsThread.h
+++ b/xpcom/threads/nsThread.h
@@ -93,7 +93,7 @@ public:
   static bool SaveMemoryReportNearOOM(ShouldSaveMemoryReport aShouldSave);
 #endif
 
-  static const char* sMainThreadRunnableName;
+  static const nsACString* sMainThreadRunnableName;
 
 private:
   void DoMainThreadSpecificProcessing(bool aReallyWait);