[tsan] Fix memcmp interceptor to correctly use COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED

[kubamracek]

Summary

The memcmp interceptor checks COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED only after it calls COMMON_INTERCEPTOR_ENTER, which causes an early process launch crash when running TSan in iOS simulator. Let's fix this by checking COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED as the very first thing in the interceptor.

compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc

 #endif
 
 #if SANITIZER_INTERCEPT_MEMCMP
 
 DECLARE_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_memcmp, uptr called_pc,
                               const void *s1, const void *s2, uptr n)
 
 INTERCEPTOR(int, memcmp, const void *a1, const void *a2, uptr size) {
-  void *ctx;
-  COMMON_INTERCEPTOR_ENTER(ctx, memcmp, a1, a2, size);
   if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
     return internal_memcmp(a1, a2, size);
+  void *ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, memcmp, a1, a2, size);
   CALL_WEAK_INTERCEPTOR_HOOK(__sanitizer_weak_hook_memcmp, GET_CALLER_PC(), a1,
                              a2, size);
   if (common_flags()->intercept_memcmp) {
     if (common_flags()->strict_memcmp) {
       // Check the entire regions even if the first bytes of the buffers are
       // different.
       COMMON_INTERCEPTOR_READ_RANGE(ctx, a1, size);
       COMMON_INTERCEPTOR_READ_RANGE(ctx, a2, size);