Always use '__thread' for Thread local storage except on MSVC

[urcu.git] / include / urcu / tls-compat.h

diff --git a/include/urcu/tls-compat.h b/include/urcu/tls-compat.h
index c17aca36b2c86a4b94f95e1c97c8aaa327f1f4a7..a2c94ded9cd9833558bb25d19b9908c6f47a9007 100644 (file)
--- a/include/urcu/tls-compat.h
+++ b/include/urcu/tls-compat.h
@@ -32,7 +32,21 @@
 extern "C" {
 #endif
 
-#ifdef CONFIG_RCU_TLS  /* Based on ax_tls.m4 */
+#ifdef CONFIG_RCU_TLS
+
+/*
+ * 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(_MSC_VER)
+# define URCU_TLS_STORAGE_CLASS        __declspec(thread)
+#else
+# define URCU_TLS_STORAGE_CLASS        __thread
+#endif
 
 /*
  * Hint: How to define/declare TLS variables of compound types
@@ -65,13 +79,13 @@ extern "C" {
  */
 
 # define DECLARE_URCU_TLS(type, name)  \
-       CONFIG_RCU_TLS type name
+       URCU_TLS_STORAGE_CLASS type name
 
 # define DEFINE_URCU_TLS(type, name)   \
-       CONFIG_RCU_TLS type name
+       URCU_TLS_STORAGE_CLASS type name
 
 # define DEFINE_URCU_TLS_INIT(type, name, init)        \
-       CONFIG_RCU_TLS type name = (init)
+       URCU_TLS_STORAGE_CLASS type name = (init)
 
 # define URCU_TLS(name)                (name)