urcu/compiler: Add urcu_static_assert

Static assertion macros copied from LTTng-ust ust-compiler.h for
compatibility with compilers that do not support static assertion.

Change-Id: I5dfa8ba565041b522a1d5c226c7a9369979a3a02
Signed-off-by: Olivier Dion <odion@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/include/urcu/compiler.h b/include/urcu/compiler.h
index 887d9be1d3f1e8ee492d225412ba884a1c79428b..197656c617d786f8af88f5648a60483ac224f3c4 100644 (file)
--- a/include/urcu/compiler.h
+++ b/include/urcu/compiler.h
@@ -193,4 +193,36 @@ volatile T cmm_cast_volatile(T t)
        })
 #endif
 
+/*
+ * Compile time assertion.
+ * - predicate: boolean expression to evaluate,
+ * - msg: string to print to the user on failure when `static_assert()` is
+ *   supported,
+ * - c_identifier_msg: message to be included in the typedef to emulate a
+ *   static assertion. This parameter must be a valid C identifier as it will
+ *   be used as a typedef name.
+ */
+#ifdef __cplusplus
+#define urcu_static_assert(predicate, msg, c_identifier_msg)  \
+       static_assert(predicate, msg)
+#elif defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
+#define urcu_static_assert(predicate, msg, c_identifier_msg)  \
+       _Static_assert(predicate, msg)
+#else
+/*
+ * Evaluates the predicate and emit a compilation error on failure.
+ *
+ * If the predicate evaluates to true, this macro emits a function
+ * prototype with an argument type which is an array of size 0.
+ *
+ * If the predicate evaluates to false, this macro emits a function
+ * prototype with an argument type which is an array of negative size
+ * which is invalid in C and forces a compiler error. The
+ * c_identifier_msg parameter is used as the argument identifier so it
+ * is printed to the user when the error is reported.
+ */
+#define urcu_static_assert(predicate, msg, c_identifier_msg)  \
+       void urcu_static_assert_proto(char c_identifier_msg[2*!!(predicate)-1])
+#endif
+
 #endif /* _URCU_COMPILER_H */

diff --git a/include/urcu/uatomic.h b/include/urcu/uatomic.h
index 5365f1fb0fdac0159edb06835f639b3045cc79eb..aca9a63da3af2d5301b92daa47fa5cdbfcedfa4b 100644 (file)
--- a/include/urcu/uatomic.h
+++ b/include/urcu/uatomic.h
@@ -5,9 +5,8 @@
 #ifndef _URCU_UATOMIC_H
 #define _URCU_UATOMIC_H
 
-#include <assert.h>
-
 #include <urcu/arch.h>
+#include <urcu/compiler.h>
 #include <urcu/config.h>
 
 enum cmm_memorder {
@@ -25,14 +24,12 @@ enum cmm_memorder {
 /*
  * Make sure that CMM_SEQ_CST_FENCE is not equivalent to other memory orders.
  */
-# ifdef static_assert
-static_assert(CMM_RELAXED == __ATOMIC_RELAXED, "");
-static_assert(CMM_CONSUME == __ATOMIC_CONSUME, "");
-static_assert(CMM_ACQUIRE == __ATOMIC_ACQUIRE, "");
-static_assert(CMM_RELEASE == __ATOMIC_RELEASE, "");
-static_assert(CMM_ACQ_REL == __ATOMIC_ACQ_REL, "");
-static_assert(CMM_SEQ_CST == __ATOMIC_SEQ_CST, "");
-# endif
+urcu_static_assert(CMM_RELAXED == __ATOMIC_RELAXED, "", cmm_relaxed);
+urcu_static_assert(CMM_CONSUME == __ATOMIC_CONSUME, "", cmm_consume);
+urcu_static_assert(CMM_ACQUIRE == __ATOMIC_ACQUIRE, "", cmm_acquire);
+urcu_static_assert(CMM_RELEASE == __ATOMIC_RELEASE, "", cmm_release);
+urcu_static_assert(CMM_ACQ_REL == __ATOMIC_ACQ_REL, "", cmm_acq_rel);
+urcu_static_assert(CMM_SEQ_CST == __ATOMIC_SEQ_CST, "", cmm_seq_cst);
 
 /*
  * This is not part of the public API. It it used internally to implement the