Keep ABI compatible with already compiled LGPL applications

[userspace-rcu.git] / urcu / tls-compat.h

diff --git a/urcu/tls-compat.h b/urcu/tls-compat.h
index fe21cb624b179f28e4a31d44a86a930b7b7c5005..34324e28c164833971ab8a9b24c39ffb16a70d3e 100644 (file)
--- a/urcu/tls-compat.h
+++ b/urcu/tls-compat.h
@@ -70,12 +70,20 @@ extern "C" {
 # define DEFINE_URCU_TLS(type, name)   \
        CONFIG_RCU_TLS type name
 
+# define __DEFINE_URCU_TLS_GLOBAL(type, name)  \
+       CONFIG_RCU_TLS type name
+
 # define URCU_TLS(name)                (name)
 
 #else /* #ifndef CONFIG_RCU_TLS */
 
 /*
  * The *_1() macros ensure macro parameters are expanded.
+ *
+ * __DEFINE_URCU_TLS_GLOBAL and __URCU_TLS_CALL exist for the sole
+ * purpose of notifying applications compiled against non-fixed 0.7 and
+ * 0.8 userspace RCU headers and using multiple flavors concurrently to
+ * recompile against fixed userspace RCU headers.
  */
 
 # include <pthread.h>
@@ -87,7 +95,8 @@ struct urcu_tls {
 };
 
 # define DECLARE_URCU_TLS_1(type, name)                                \
-       type *__tls_access_ ## name(void)
+       type *__tls_access2_ ## name(void)
+
 # define DECLARE_URCU_TLS(type, name)                          \
        DECLARE_URCU_TLS_1(type, name)
 
@@ -95,8 +104,14 @@ struct urcu_tls {
  * Note: we don't free memory at process exit, since it will be dealt
  * with by the OS.
  */
+# define __URCU_TLS_CALL_1(name)                               \
+       __tls_access2_ ## name
+
+# define __URCU_TLS_CALL(name)                                 \
+       __URCU_TLS_CALL_1(name)
+
 # define DEFINE_URCU_TLS_1(type, name)                         \
-       type *__tls_access_ ## name(void)                       \
+       type *__tls_access2_ ## name(void)                      \
        {                                                       \
                static struct urcu_tls __tls_ ## name = {       \
                        .init_mutex = PTHREAD_MUTEX_INITIALIZER,\
@@ -124,10 +139,32 @@ struct urcu_tls {
                return __tls_p;                                 \
        }
 
+/*
+ * Define with an without macro expansion to handle erroneous callers.
+ * Trigger an abort() if the caller application uses the clashing symbol
+ * if a weak symbol is overridden.
+ */
+# define __DEFINE_URCU_TLS_GLOBAL(type, name)                  \
+       DEFINE_URCU_TLS_1(type, name)                           \
+       int __urcu_tls_symbol_refcount_ ## name __attribute__((weak)); \
+       static __attribute__((constructor))                     \
+       void __urcu_tls_inc_refcount_ ## name(void)             \
+       {                                                       \
+               __urcu_tls_symbol_refcount_ ## name++;          \
+       }                                                       \
+       type *__tls_access_ ## name(void)                       \
+       {                                                       \
+               if (__urcu_tls_symbol_refcount_ ## name > 1) {  \
+                       fprintf(stderr, "Error: Userspace RCU symbol clash for multiple concurrent flavors. Please upgrade liburcu libraries and headers, then recompile your application.\n"); \
+                       abort();                                \
+               }                                               \
+               return __URCU_TLS_CALL(name)();                 \
+       }
+
 # define DEFINE_URCU_TLS(type, name)                           \
        DEFINE_URCU_TLS_1(type, name)
 
-# define URCU_TLS_1(name)      (*__tls_access_ ## name())
+# define URCU_TLS_1(name)      (*__tls_access2_ ## name())
 
 # define URCU_TLS(name)                URCU_TLS_1(name)