Author: ed
Date: Mon May 13 21:46:07 2013
New Revision: 250623
URL: http://svnweb.freebsd.org/changeset/base/250623
Log:
Rework the way C11 keywords are defined.
Instead of only checking the __STDC_VERSION__, we can also use Clang's
__has_extension() to check for features specifically. This allows us to,
say, use Clang's native _Static_assert() instead of the typedef hack,
making the compiler error messages a lot more readable.
Reviewed by: theraven
Modified:
head/sys/sys/cdefs.h
Modified: head/sys/sys/cdefs.h
==============================================================================
--- head/sys/sys/cdefs.h Mon May 13 21:44:59 2013 (r250622)
+++ head/sys/sys/cdefs.h Mon May 13 21:46:07 2013 (r250623)
@@ -36,6 +36,23 @@
#ifndef _SYS_CDEFS_H_
#define _SYS_CDEFS_H_
+/*
+ * Testing against Clang-specific extensions.
+ */
+
+#ifndef __has_extension
+#define __has_extension __has_feature
+#endif
+#ifndef __has_feature
+#define __has_feature(x) 0
+#endif
+#ifndef __has_include
+#define __has_include(x) 0
+#endif
+#ifndef __has_builtin
+#define __has_builtin(x) 0
+#endif
+
#if defined(__cplusplus)
#define __BEGIN_DECLS extern "C" {
#define __END_DECLS }
@@ -232,22 +249,36 @@
/*
* Keywords added in C11.
*/
-#if defined(__cplusplus) && __cplusplus >= 201103L
-#define _Alignas(e) alignas(e)
-#define _Alignof(e) alignof(e)
-#define _Noreturn [[noreturn]]
-#define _Static_assert(e, s) static_assert(e, s)
-/* FIXME: change this to thread_local when clang in base supports it */
-#define _Thread_local __thread
-#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
-/* Do nothing. They are language keywords. */
+
+#if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 201112L
+
+#if !__has_extension(c_alignas)
+#if (defined(__cplusplus) && __cplusplus >= 201103L) || \
+ __has_extension(cxx_alignas)
+#define _Alignas(x) alignas(x)
#else
-/* Not supported. Implement them using our versions. */
+/* XXX: Only emulates _Alignas(constant-expression); not _Alignas(type-name).
*/
#define _Alignas(x) __aligned(x)
+#endif
+#endif
+
+#if defined(__cplusplus) && __cplusplus >= 201103L
+#define _Alignof(x) alignof(x)
+#else
#define _Alignof(x) __alignof(x)
+#endif
+
+#if defined(__cplusplus) && __cplusplus >= 201103L
+#define _Noreturn [[noreturn]]
+#else
#define _Noreturn __dead2
-#define _Thread_local __thread
-#ifdef __COUNTER__
+#endif
+
+#if !__has_extension(c_static_assert)
+#if (defined(__cplusplus) && __cplusplus >= 201103L) || \
+ __has_extension(cxx_static_assert)
+#define _Static_assert(x, y) static_assert(x, y)
+#elif defined(__COUNTER__)
#define _Static_assert(x, y) __Static_assert(x, __COUNTER__)
#define __Static_assert(x, y) ___Static_assert(x, y)
#define ___Static_assert(x, y) typedef char __assert_ ## y[(x) ? 1 :
-1]
@@ -256,6 +287,20 @@
#endif
#endif
+#if !__has_extension(c_thread_local)
+/* XXX: Change this to test against C++11 when clang in base supports it. */
+#if /* (defined(__cplusplus) && __cplusplus >= 201103L) || */ \
+ __has_extension(cxx_thread_local)
+#define _Thread_local thread_local
+#elif defined(lint)
+#define _Thread_local
+#else
+#define _Thread_local __thread
+#endif
+#endif
+
+#endif /* __STDC_VERSION__ || __STDC_VERSION__ < 201112L */
+
/*
* Emulation of C11 _Generic(). Unlike the previously defined C11
* keywords, it is not possible to implement this using exactly the same
@@ -682,19 +727,6 @@
#endif
#endif
-#ifndef __has_extension
-#define __has_extension __has_feature
-#endif
-#ifndef __has_feature
-#define __has_feature(x) 0
-#endif
-#ifndef __has_include
-#define __has_include(x) 0
-#endif
-#ifndef __has_builtin
-#define __has_builtin(x) 0
-#endif
-
#if defined(__mips) || defined(__powerpc64__)
#define __NO_TLS 1
#endif
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