Bug 1436768 - Add debug code to LazyLogModule. r=froydnj

--HG--
extra : rebase_source : bd70f788eb986b73eb70460337d5d7c3423c4e8a
extra : source : 82ef13b02416c8519178a7e8e08791b7b8dfcbdb

mfbt/Poison.h

@@ -81,8 +81,9 @@ namespace mozilla {
  */
 class CorruptionCanary {
 public:
-  CorruptionCanary() {
+  constexpr CorruptionCanary()
-    mValue = kCanarySet;
+    : mValue(kCanarySet)
+  {
   }
 
   ~CorruptionCanary() {

xpcom/base/Logging.cpp

@@ -56,6 +56,8 @@ LazyLogModule::operator LogModule*()
     mLog = tmp;
   }
 
+  mCanary.Check();
+
   return tmp;
 }
 

xpcom/base/Logging.h

@@ -14,6 +14,7 @@
 #include "mozilla/Atomics.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/Likely.h"
+#include "mozilla/Poison.h"
 
 // We normally have logging enabled everywhere, but measurements showed that
 // having logging enabled on Android is quite expensive (hundreds of kilobytes
@@ -174,6 +175,7 @@ public:
 
 private:
   const char* const mLogName;
+  CorruptionCanary mCanary;
   Atomic<LogModule*, ReleaseAcquire> mLog;
 };