1From 2e359284497c361e3208501fc70d49b2c54dc4ef Mon Sep 17 00:00:00 2001
2From: Michael Jeanson <mjeanson@efficios.com>
3Date: Tue, 14 Sep 2021 10:41:08 -0400
4Subject: [PATCH] Always use '__thread' for Thread local storage except on MSVC
5
6Use the GCC extension '__thread' [1] for Thread local storage on all C
7and C++ compilers except MSVC.
8
9While C11 and C++11 respectively offer '_Thread_local' and
10'thread_local' as potentialy faster implementations, they offer no
11guarantees of compatibility when used in a library interface which might
12be used by both C and C++ client code.
13
14[1] https://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html
15
16Change-Id: If4fe8bcdbda24b21dedf382112bd5c5f836c00c8
17Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
18Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
19
20[Retrieved from:
21https://github.com/urcu/userspace-rcu/commit/2e359284497c361e3208501fc70d49b2c54dc4ef]
22Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
23---
24 include/urcu/tls-compat.h | 15 +++++++--------
25 1 file changed, 7 insertions(+), 8 deletions(-)
26
27diff --git a/include/urcu/tls-compat.h b/include/urcu/tls-compat.h
28index 25cf375a..a2c94ded 100644
29--- a/include/urcu/tls-compat.h
30+++ b/include/urcu/tls-compat.h
31@@ -35,15 +35,14 @@ extern "C" {
32 #ifdef CONFIG_RCU_TLS
33
34 /*
35- * Don't use C++ 'thread_local' on MacOs, the implementation is incompatible
36- * with C and will result in a link error when accessing an extern variable
37- * provided by the C library from C++ code.
38+ * Default to '__thread' on all C and C++ compilers except MSVC. While C11 has
39+ * '_Thread_local' and C++11 has 'thread_local', only '__thread' seems to have
40+ * a compatible implementation when linking public extern symbols across
41+ * language boundaries.
42+ *
43+ * For more details, see 'https://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html'.
44  */
45-#if defined (__cplusplus) && (__cplusplus >= 201103L) && !defined(__APPLE__)
46-# define URCU_TLS_STORAGE_CLASS	thread_local
47-#elif defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
48-# define URCU_TLS_STORAGE_CLASS	_Thread_local
49-#elif defined (_MSC_VER)
50+#if defined(_MSC_VER)
51 # define URCU_TLS_STORAGE_CLASS	__declspec(thread)
52 #else
53 # define URCU_TLS_STORAGE_CLASS	__thread
54