From 2e359284497c361e3208501fc70d49b2c54dc4ef Mon Sep 17 00:00:00 2001 From: Michael Jeanson Date: Tue, 14 Sep 2021 10:41:08 -0400 Subject: [PATCH] Always use '__thread' for Thread local storage except on MSVC Use the GCC extension '__thread' [1] for Thread local storage on all C and C++ compilers except MSVC. While C11 and C++11 respectively offer '_Thread_local' and 'thread_local' as potentialy faster implementations, they offer no guarantees of compatibility when used in a library interface which might be used by both C and C++ client code. [1] https://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html Change-Id: If4fe8bcdbda24b21dedf382112bd5c5f836c00c8 Signed-off-by: Michael Jeanson Signed-off-by: Mathieu Desnoyers [Retrieved from: https://github.com/urcu/userspace-rcu/commit/2e359284497c361e3208501fc70d49b2c54dc4ef] Signed-off-by: Fabrice Fontaine --- include/urcu/tls-compat.h | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/include/urcu/tls-compat.h b/include/urcu/tls-compat.h index 25cf375a..a2c94ded 100644 --- a/include/urcu/tls-compat.h +++ b/include/urcu/tls-compat.h @@ -35,15 +35,14 @@ extern "C" { #ifdef CONFIG_RCU_TLS /* - * Don't use C++ 'thread_local' on MacOs, the implementation is incompatible - * with C and will result in a link error when accessing an extern variable - * provided by the C library from C++ code. + * Default to '__thread' on all C and C++ compilers except MSVC. While C11 has + * '_Thread_local' and C++11 has 'thread_local', only '__thread' seems to have + * a compatible implementation when linking public extern symbols across + * language boundaries. + * + * For more details, see 'https://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html'. */ -#if defined (__cplusplus) && (__cplusplus >= 201103L) && !defined(__APPLE__) -# define URCU_TLS_STORAGE_CLASS thread_local -#elif defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L) -# define URCU_TLS_STORAGE_CLASS _Thread_local -#elif defined (_MSC_VER) +#if defined(_MSC_VER) # define URCU_TLS_STORAGE_CLASS __declspec(thread) #else # define URCU_TLS_STORAGE_CLASS __thread