Fix false positive in tsan (fixes #4755)

Author: vitaut

include/fmt/format-inl.h

@@ -8,6 +8,11 @@
 #ifndef FMT_FORMAT_INL_H_
 #define FMT_FORMAT_INL_H_
 
+#ifdef __SANITIZE_THREAD__
+extern "C" void __tsan_acquire(void*);
+extern "C" void __tsan_release(void*);
+#endif
+
 #ifndef FMT_MODULE
 #  include <stddef.h>  // ptrdiff_t
 
@@ -1696,6 +1701,9 @@ class file_print_buffer<F, enable_if_t<has_flockfile<F>::value>>
  public:
   explicit file_print_buffer(F* f) : buffer(grow, size_t()), file_(f) {
     flockfile(f);
+#ifdef __SANITIZE_THREAD__
+    __tsan_acquire(f);
+#endif
     file_.init_buffer();
     auto buf = file_.get_write_buffer();
     set(buf.data, buf.size);
@@ -1705,6 +1713,9 @@ class file_print_buffer<F, enable_if_t<has_flockfile<F>::value>>
     bool flush = file_.needs_flush();
     F* f = file_;    // Make funlockfile depend on the template parameter F
     funlockfile(f);  // for the system API detection to work.
+#ifdef __SANITIZE_THREAD__
+    __tsan_release(f);
+#endif
     if (flush) fflush(file_);
   }
 };