Add support for C11 static_assert and thread_local

Tested with Clang, GCC 4.5 & up, ICC 17 and MSVC 2017. No current
version of MSVC supports C11 and GCC implemented the features slightly
later in C than in C++.

Change-Id: I57a1bd6e0c194530b732fffd14f45c5074c9a052
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

2 files changed, 56 insertions, 26 deletions

diff --git a/src/corelib/global/qcompilerdetection.h b/src/corelib/global/qcompilerdetection.h
index 2c58ff87e9..e4b756f4b7 100644
--- a/src/corelib/global/qcompilerdetection.h
+++ b/src/corelib/global/qcompilerdetection.h
@@ -651,6 +651,12 @@
 #        undef Q_COMPILER_CONSTEXPR
 #      endif
 #    endif
+#  elif defined(__STDC_VERSION__) && __STDC_VERSION__ > 199901L s
+//   C11 features supported. Only tested with ICC 17 and up.
+#    define Q_COMPILER_STATIC_ASSERT
+#    if __has_include(<threads.h>)
+#      define Q_COMPILER_THREAD_LOCAL
+#    endif
 #  endif
 #endif
 
@@ -803,6 +809,17 @@
 #    endif
 #  endif
 
+#  if defined(__STDC_VERSION__)
+#    if __has_feature(c_static_assert)
+#      define Q_COMPILER_STATIC_ASSERT
+#    endif
+#    if __has_feature(c_thread_local) && __has_include(<threads.h>)
+#      if !defined(__FreeBSD__) /* FreeBSD clang fails on __cxa_thread_atexit */
+#        define Q_COMPILER_THREAD_LOCAL
+#      endif
+#    endif
+#  endif
+
 #  if defined(__has_warning)
 #    if __has_warning("-Wunused-private-field")
 #      define Q_DECL_UNUSED_MEMBER Q_DECL_UNUSED
@@ -898,6 +915,18 @@
 #      define Q_COMPILER_RETURN_TYPE_DEDUCTION
 #    endif
 #  endif
+#  if defined(__STDC_VERSION__) && __STDC_VERSION__ > 199901L
+#    if Q_CC_GNU >= 407
+       /* C11 features supported in GCC 4.7: */
+#      define Q_COMPILER_STATIC_ASSERT
+#    endif
+#    if Q_CC_GNU >= 409
+       /* C11 features supported in GCC 4.9: */
+#      if __has_include(<threads.h>)
+#        define Q_COMPILER_THREAD_LOCAL
+#      endif
+#    endif
+#  endif
 #endif
 
 #if defined(Q_CC_MSVC)
diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
index e49bace002..33b86a7321 100644
--- a/src/corelib/global/qglobal.h
+++ b/src/corelib/global/qglobal.h
@@ -47,6 +47,7 @@
 #  include <utility>
 #endif
 #ifndef __ASSEMBLER__
+#  include <assert.h>
 #  include <stddef.h>
 #endif
 
@@ -105,6 +106,32 @@
 #  define Q_OF_MACH_O
 #endif
 
+/*
+   Avoid "unused parameter" warnings
+*/
+#define Q_UNUSED(x) (void)x;
+
+#if defined(__cplusplus) && defined(Q_COMPILER_STATIC_ASSERT)
+#  define Q_STATIC_ASSERT(Condition) static_assert(bool(Condition), #Condition)
+#  define Q_STATIC_ASSERT_X(Condition, Message) static_assert(bool(Condition), Message)
+#elif defined(Q_COMPILER_STATIC_ASSERT)
+// C11 mode - using the _S version in case <assert.h> doesn't do the right thing
+#  define Q_STATIC_ASSERT(Condition) _Static_assert(!!(Condition), #Condition)
+#  define Q_STATIC_ASSERT_X(Condition, Message) _Static_assert(!!(Condition), Message)
+#else
+// C89 & C99 version
+#  define Q_STATIC_ASSERT_PRIVATE_JOIN(A, B) Q_STATIC_ASSERT_PRIVATE_JOIN_IMPL(A, B)
+#  define Q_STATIC_ASSERT_PRIVATE_JOIN_IMPL(A, B) A ## B
+#  ifdef __COUNTER__
+#  define Q_STATIC_ASSERT(Condition) \
+    typedef char Q_STATIC_ASSERT_PRIVATE_JOIN(q_static_assert_result, __COUNTER__) [(Condition) ? 1 : -1];
+#  else
+#  define Q_STATIC_ASSERT(Condition) \
+    typedef char Q_STATIC_ASSERT_PRIVATE_JOIN(q_static_assert_result, __LINE__) [(Condition) ? 1 : -1];
+#  endif /* __COUNTER__ */
+#  define Q_STATIC_ASSERT_X(Condition, Message) Q_STATIC_ASSERT(Condition)
+#endif
+
 #ifdef __cplusplus
 
 #include <algorithm>
@@ -688,11 +715,6 @@ Q_CORE_EXPORT Q_DECL_CONST_FUNCTION bool qSharedBuild() Q_DECL_NOTHROW;
 #endif
 
 /*
-   Avoid "unused parameter" warnings
-*/
-#define Q_UNUSED(x) (void)x;
-
-/*
    Debugging and error handling
 */
 
@@ -750,27 +772,6 @@ Q_CORE_EXPORT void qt_assert_x(const char *where, const char *what, const char *
 #  endif
 #endif
 
-
-#ifdef Q_COMPILER_STATIC_ASSERT
-#define Q_STATIC_ASSERT(Condition) static_assert(bool(Condition), #Condition)
-#define Q_STATIC_ASSERT_X(Condition, Message) static_assert(bool(Condition), Message)
-#else
-// Intentionally undefined
-template <bool Test> class QStaticAssertFailure;
-template <> class QStaticAssertFailure<true> {};
-
-#define Q_STATIC_ASSERT_PRIVATE_JOIN(A, B) Q_STATIC_ASSERT_PRIVATE_JOIN_IMPL(A, B)
-#define Q_STATIC_ASSERT_PRIVATE_JOIN_IMPL(A, B) A ## B
-#ifdef __COUNTER__
-#define Q_STATIC_ASSERT(Condition) \
-    enum {Q_STATIC_ASSERT_PRIVATE_JOIN(q_static_assert_result, __COUNTER__) = sizeof(QStaticAssertFailure<!!(Condition)>)}
-#else
-#define Q_STATIC_ASSERT(Condition) \
-    enum {Q_STATIC_ASSERT_PRIVATE_JOIN(q_static_assert_result, __LINE__) = sizeof(QStaticAssertFailure<!!(Condition)>)}
-#endif /* __COUNTER__ */
-#define Q_STATIC_ASSERT_X(Condition, Message) Q_STATIC_ASSERT(Condition)
-#endif
-
 Q_NORETURN Q_CORE_EXPORT void qt_check_pointer(const char *, int) Q_DECL_NOTHROW;
 Q_CORE_EXPORT void qBadAlloc();