Change internal_start_thread arguments to match pthread_create.

This avoids a CFI-unfriendly function pointer type cast in
internal_start_thread.

compiler-rt/lib/sanitizer_common/sanitizer_common.h

@@ -855,7 +855,7 @@ INLINE uptr GetPthreadDestructorIterations() {
 #endif
 }
 
-void *internal_start_thread(void(*func)(void*), void *arg);
+void *internal_start_thread(void *(*func)(void*), void *arg);
 void internal_join_thread(void *th);
 void MaybeStartBackgroudThread();
 

compiler-rt/lib/sanitizer_common/sanitizer_common_libcdep.cpp

@@ -30,7 +30,7 @@ SANITIZER_WEAK_ATTRIBUTE StackDepotStats *StackDepotGetStats() {
   return nullptr;
 }
 
-void BackgroundThread(void *arg) {
+void *BackgroundThread(void *arg) {
   const uptr hard_rss_limit_mb = common_flags()->hard_rss_limit_mb;
   const uptr soft_rss_limit_mb = common_flags()->soft_rss_limit_mb;
   const bool heap_profile = common_flags()->heap_profile;

compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp

@@ -1701,7 +1701,7 @@ HandleSignalMode GetHandleSignalMode(int signum) {
 }
 
 #if !SANITIZER_GO
-void *internal_start_thread(void(*func)(void *arg), void *arg) {
+void *internal_start_thread(void *(*func)(void *arg), void *arg) {
   // Start the thread with signals blocked, otherwise it can steal user signals.
   __sanitizer_sigset_t set, old;
   internal_sigfillset(&set);
@@ -1712,7 +1712,7 @@ void *internal_start_thread(void(*func)(void *arg), void *arg) {
 #endif
   internal_sigprocmask(SIG_SETMASK, &set, &old);
   void *th;
-  real_pthread_create(&th, nullptr, (void*(*)(void *arg))func, arg);
+  real_pthread_create(&th, nullptr, func, arg);
   internal_sigprocmask(SIG_SETMASK, &old, nullptr);
   return th;
 }
@@ -1721,7 +1721,7 @@ void internal_join_thread(void *th) {
   real_pthread_join(th, nullptr);
 }
 #else
-void *internal_start_thread(void (*func)(void *), void *arg) { return 0; }
+void *internal_start_thread(void *(*func)(void *), void *arg) { return 0; }
 
 void internal_join_thread(void *th) {}
 #endif

compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

@@ -677,13 +677,13 @@ uptr GetRSS() {
   return info.resident_size;
 }
 
-void *internal_start_thread(void(*func)(void *arg), void *arg) {
+void *internal_start_thread(void *(*func)(void *arg), void *arg) {
   // Start the thread with signals blocked, otherwise it can steal user signals.
   __sanitizer_sigset_t set, old;
   internal_sigfillset(&set);
   internal_sigprocmask(SIG_SETMASK, &set, &old);
   pthread_t th;
-  pthread_create(&th, 0, (void*(*)(void *arg))func, arg);
+  pthread_create(&th, 0, func, arg);
   internal_sigprocmask(SIG_SETMASK, &old, 0);
   return th;
 }

compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_mac.cpp

@@ -50,7 +50,7 @@ struct RunThreadArgs {
   void *argument;
 };
 
-void RunThread(void *arg) {
+void *RunThread(void *arg) {
   struct RunThreadArgs *run_args = (struct RunThreadArgs *)arg;
   SuspendedThreadsListMac suspended_threads_list;
 
@@ -59,7 +59,7 @@ void RunThread(void *arg) {
   kern_return_t err = task_threads(mach_task_self(), &threads, &num_threads);
   if (err != KERN_SUCCESS) {
     VReport(1, "Failed to get threads for task (errno %d).\n", err);
-    return;
+    return nullptr;
   }
 
   thread_t thread_self = mach_thread_self();
@@ -76,6 +76,7 @@ void RunThread(void *arg) {
   for (unsigned int i = 0; i < num_suspended; ++i) {
     thread_resume(suspended_threads_list.GetThread(i));
   }
+  return nullptr;
 }
 
 void StopTheWorld(StopTheWorldCallback callback, void *argument) {

compiler-rt/lib/sanitizer_common/sanitizer_win.cpp

@@ -787,7 +787,7 @@ uptr GetRSS() {
   return counters.WorkingSetSize;
 }
 
-void *internal_start_thread(void (*func)(void *arg), void *arg) { return 0; }
+void *internal_start_thread(void *(*func)(void *arg), void *arg) { return 0; }
 void internal_join_thread(void *th) { }
 
 // ---------------------- BlockingMutex ---------------- {{{1

compiler-rt/lib/tsan/rtl/tsan_rtl.cpp

@@ -144,7 +144,7 @@ static void MemoryProfiler(Context *ctx, fd_t fd, int i) {
   WriteToFile(fd, buf.data(), internal_strlen(buf.data()));
 }
 
-static void BackgroundThread(void *arg) {
+static void *BackgroundThread(void *arg) {
   // This is a non-initialized non-user thread, nothing to see here.
   // We don't use ScopedIgnoreInterceptors, because we want ignores to be
   // enabled even when the thread function exits (e.g. during pthread thread
@@ -220,6 +220,7 @@ static void BackgroundThread(void *arg) {
       }
     }
   }
+  return nullptr;
 }
 
 static void StartBackgroundThread() {