Export of internal Abseil changes

--
cbd86b318ce206d1fe9eb001979b8d2efe57e5fa by Derek Mauro <dmauro@google.com>:

Stop inlining `CurrentThreadIdentityIfPresent()` on Apple platforms

In some build configurations the Apple linker rejects thread_local
variables exposed in headers

Fixes #954
Fixes #965

PiperOrigin-RevId: 375930997
GitOrigin-RevId: e34600e09f748b686d20a4f729ae914ebfd9e7bf
Change-Id: I9fcd2f02bd6abdea3ed412217e1be18f2c7bf762

1 files changed, 11 insertions, 6 deletions

diff --git a/absl/base/internal/thread_identity.h b/absl/base/internal/thread_identity.h
index 9ee651a3..6e25b92f 100644
--- a/absl/base/internal/thread_identity.h
+++ b/absl/base/internal/thread_identity.h
@@ -236,13 +236,18 @@ ABSL_CONST_INIT extern thread_local ThreadIdentity* thread_identity_ptr;
 #error Thread-local storage not detected on this platform
 #endif
 
-// thread_local variables cannot be in headers exposed by DLLs. However, it is
-// important for performance reasons in general that
-// `CurrentThreadIdentityIfPresent` be inlined. This is not possible across a
-// DLL boundary so, with DLLs, we opt to have the function not be inlined. Note
+// thread_local variables cannot be in headers exposed by DLLs or in certain
+// build configurations on Apple platforms. However, it is important for
+// performance reasons in general that `CurrentThreadIdentityIfPresent` be
+// inlined. In the other cases we opt to have the function not be inlined. Note
 // that `CurrentThreadIdentityIfPresent` is declared above so we can exclude
-// this entire inline definition when compiling as a DLL.
-#if !defined(ABSL_BUILD_DLL) && !defined(ABSL_CONSUME_DLL)
+// this entire inline definition.
+#if !defined(__APPLE__) && !defined(ABSL_BUILD_DLL) && \
+    !defined(ABSL_CONSUME_DLL)
+#define ABSL_INTERNAL_INLINE_CURRENT_THREAD_IDENTITY_IF_PRESENT 1
+#endif
+
+#ifdef ABSL_INTERNAL_INLINE_CURRENT_THREAD_IDENTITY_IF_PRESENT
 inline ThreadIdentity* CurrentThreadIdentityIfPresent() {
   return thread_identity_ptr;
 }