[tsan] Fix __cxa_guard_* interceptors on OS X

[kubamracek]

Summary

This patch fixes the __cxa_guard_acquire, __cxa_guard_release and __cxa_guard_abort interceptors on OS X. They apparently work on Linux just by having the same name, but on OS X, we actually need to use TSAN_INTERCEPTOR.

[dvyukov]

lib/tsan/rtl/tsan_interceptors.cc

790 ↗

(On Diff #40763)

I think this will break statically-linked libstdc++ (which we do have in some contexts).
Linux interceptors are especially defined as weak functions (so that they don't cause link errors when user defines them as well). So they silently auto-disable themselves when such symbol is already present in the binary.
If we link libstdc++ statically, it will bring own __cxa_guard_acquire which will silently replace our interceptor.
I have not tested it, though.

[kubamracek]

I see. Changing patch to use #ifdef to use TSAN_INTERCEPTOR on OS X, and the current way on other platforms.

[dvyukov]

LGTM with a nit

lib/tsan/rtl/tsan_interceptors.cc

789 ↗

(On Diff #40773)

please add a comment for future generations as to why we are doing this

compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc

 #if !SANITIZER_MAC
 TSAN_INTERCEPTOR(int, posix_memalign, void **memptr, uptr align, uptr sz) {
   SCOPED_INTERCEPTOR_RAW(posix_memalign, memptr, align, sz);
   *memptr = user_alloc(thr, pc, sz, align);
   return 0;
 }
 #endif
 
+// __cxa_guard_acquire and friends need to be intercepted in a special way -
+// regular interceptors will break statically-linked libstdc++. Linux
+// interceptors are especially defined as weak functions (so that they don't
+// cause link errors when user defines them as well). So they silently
+// auto-disable themselves when such symbol is already present in the binary. If
+// we link libstdc++ statically, it will bring own __cxa_guard_acquire which
+// will silently replace our interceptor.  That's why on Linux we simply export
+// these interceptors with INTERFACE_ATTRIBUTE.
+// On OS X, we don't support statically linking, so we just use a regular
+// interceptor.
+#if SANITIZER_MAC
+#define STDCXX_INTERCEPTOR TSAN_INTERCEPTOR
+#else
+#define STDCXX_INTERCEPTOR(rettype, name, ...) \
+  extern "C" rettype INTERFACE_ATTRIBUTE name(__VA_ARGS__)
+#endif
+
 // Used in thread-safe function static initialization.
-extern "C" int INTERFACE_ATTRIBUTE __cxa_guard_acquire(atomic_uint32_t *g) {
+STDCXX_INTERCEPTOR(int, __cxa_guard_acquire, atomic_uint32_t *g) {
   SCOPED_INTERCEPTOR_RAW(__cxa_guard_acquire, g);
   for (;;) {
     u32 cmp = atomic_load(g, memory_order_acquire);
     if (cmp == 0) {
       if (atomic_compare_exchange_strong(g, &cmp, 1<<16, memory_order_relaxed))
         return 1;
     } else if (cmp == 1) {
       Acquire(thr, pc, (uptr)g);
       return 0;
     } else {
       internal_sched_yield();
     }
   }
 }
 
-extern "C" void INTERFACE_ATTRIBUTE __cxa_guard_release(atomic_uint32_t *g) {
+STDCXX_INTERCEPTOR(void, __cxa_guard_release, atomic_uint32_t *g) {
   SCOPED_INTERCEPTOR_RAW(__cxa_guard_release, g);
   Release(thr, pc, (uptr)g);
   atomic_store(g, 1, memory_order_release);
 }
 
-extern "C" void INTERFACE_ATTRIBUTE __cxa_guard_abort(atomic_uint32_t *g) {
+STDCXX_INTERCEPTOR(void, __cxa_guard_abort, atomic_uint32_t *g) {
   SCOPED_INTERCEPTOR_RAW(__cxa_guard_abort, g);
   atomic_store(g, 0, memory_order_relaxed);
 }
 
 namespace __tsan {
 void DestroyThreadState() {
   ThreadState *thr = cur_thread();
   ThreadFinish(thr);