Bug 1397505 - Only support dumping/resetting coverage counters with GCC builds. r=froydnj

tools/code-coverage/CodeCoverageHandler.cpp

@@ -16,13 +16,31 @@ using namespace mozilla::ipc;
 
 // The __gcov_dump function writes the coverage counters to gcda files.
 // The __gcov_reset function resets the coverage counters to zero.
-// They are defined at https://github.com/gcc-mirror/gcc/blob/aad93da1a579b9ae23ede6b9cf8523360f0a08b4/libgcc/libgcov-interface.c
+// They are defined at https://github.com/gcc-mirror/gcc/blob/aad93da1a579b9ae23ede6b9cf8523360f0a08b4/libgcc/libgcov-interface.c.
 // __gcov_flush is protected by a mutex, __gcov_dump and __gcov_reset aren't.
 // So we are using a CrossProcessMutex to protect them.
 
+#if defined(__GNUC__) && !defined(__clang__)
 extern "C" void __gcov_dump();
 extern "C" void __gcov_reset();
 
+void counters_dump() {
+  __gcov_dump();
+}
+
+void counters_reset() {
+  __gcov_reset();
+}
+#else
+void counters_dump() {
+  /* Do nothing */
+}
+
+void counters_reset() {
+  /* Do nothing */
+}
+#endif
+
 StaticAutoPtr<CodeCoverageHandler> CodeCoverageHandler::instance;
 
 void CodeCoverageHandler::DumpCounters(int)
@@ -30,7 +48,7 @@ void CodeCoverageHandler::DumpCounters(int)
   CrossProcessMutexAutoLock lock(*CodeCoverageHandler::Get()->GetMutex());
 
   printf_stderr("[CodeCoverage] Requested dump.\n");
-  __gcov_dump();
+  counters_dump();
   printf_stderr("[CodeCoverage] Dump completed.\n");
 }
 
@@ -39,7 +57,7 @@ void CodeCoverageHandler::ResetCounters(int)
   CrossProcessMutexAutoLock lock(*CodeCoverageHandler::Get()->GetMutex());
 
   printf_stderr("[CodeCoverage] Requested reset.\n");
-  __gcov_reset();
+  counters_reset();
   printf_stderr("[CodeCoverage] Reset completed.\n");
 }