clang: Use __has_feature() to detect C++11 features

Apple's clang version is often reported as the next official clang
version, but Apple clang does not support all the features that the
final official clang does. Instead of using version based feature
detection, use the __has_feature() built-in instead, so that we
correctly #define the various Q_COMPILER_* macros.

Task-number: QTBUG-25554
Change-Id: I2195401dbf6cd8574c30aa1bd6f7cf1cf537dae7
Reviewed-by: Morten Johan Sørvig <morten.sorvig@nokia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 74 insertions, 21 deletions

diff --git a/src/corelib/global/qcompilerdetection.h b/src/corelib/global/qcompilerdetection.h
index a971bfdf12..c55da5c144 100644
--- a/src/corelib/global/qcompilerdetection.h
+++ b/src/corelib/global/qcompilerdetection.h
@@ -449,7 +449,8 @@
  *  N2541           Q_COMPILER_AUTO_FUNCTION
  *  N1984 N2546     Q_COMPILER_AUTO_TYPE
  *  N2437           Q_COMPILER_CLASS_ENUM
- *  N2235 N3276     Q_COMPILER_DECLTYPE
+ *  N2235           Q_COMPILER_CONSTEXPR
+ *  N2343 N3276     Q_COMPILER_DECLTYPE
  *  N2346           Q_COMPILER_DEFAULT_DELETE_MEMBERS
  *  N1986           Q_COMPILER_DELEGATING_CONSTRUCTORS
  *  N3206 N3272     Q_COMPILER_EXPLICIT_OVERRIDES   (v0.9 and above only)
@@ -466,7 +467,7 @@
  *  N1720           Q_COMPILER_STATIC_ASSERT
  *  N2258           Q_COMPILER_TEMPLATE_ALIAS
  *  N2659           Q_COMPILER_THREAD_LOCAL
- *  N2756           Q_COMPILER_UDL
+ *  N2765           Q_COMPILER_UDL
  *  N2442           Q_COMPILER_UNICODE_STRINGS
  *  N2544           Q_COMPILER_UNRESTRICTED_UNIONS
  *  N1653           Q_COMPILER_VARIADIC_MACROS
@@ -512,42 +513,94 @@
 #  if !__has_feature(cxx_rtti)
 #    define QT_NO_RTTI
 #  endif
+
 /* C++11 features, see http://clang.llvm.org/cxx_status.html */
 #  if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
-#    if ((__clang_major__ * 100) + __clang_minor__) >= 209 /* since clang 2.9 */
+    /* Detect C++ features using __has_feature(), see http://clang.llvm.org/docs/LanguageExtensions.html#cxx11 */
+#    if __has_feature(cxx_alignas)
+#      define Q_COMPILER_ALIGNAS
+#      define Q_COMPILER_ALIGNOF
+#    endif
+#    if 0 /* not implemented in clang yet */
+#     define Q_COMPILER_ATOMICS
+#    endif
+#    if __has_feature(cxx_attributes)
+#      define Q_COMPILER_ATTRIBUTES
+#    endif
+#    if __has_feature(cxx_auto_type)
+#      define Q_COMPILER_AUTO_FUNCTION
 #      define Q_COMPILER_AUTO_TYPE
-#      define Q_COMPILER_DECLTYPE
-#      define Q_COMPILER_EXTERN_TEMPLATES
-#      define Q_COMPILER_RVALUE_REFS
-#      define Q_COMPILER_STATIC_ASSERT
-#      define Q_COMPILER_VARIADIC_MACROS
-#      define Q_COMPILER_VARIADIC_TEMPLATES
 #    endif
-#    if ((__clang_major__ * 100) + __clang_minor__) >= 300 /* since clang 3.0 */
+#    if __has_feature(cxx_strong_enums)
 #      define Q_COMPILER_CLASS_ENUM
-        /* defaulted members in 3.0, deleted members in 2.9 */
+#    endif
+#    if __has_feature(cxx_constexpr)
+#      define Q_COMPILER_CONSTEXPR
+#    endif
+#    if __has_feature(cxx_decltype) /* && __has_feature(cxx_decltype_incomplete_return_types) */
+#      define Q_COMPILER_DECLTYPE
+#    endif
+#    if __has_feature(cxx_defaulted_functions) && __has_feature(cxx_deleted_functions) /* defaulted members in 3.0, deleted members in 2.9 */
 #      define Q_COMPILER_DEFAULT_DELETE_MEMBERS
+#    endif
+#    if __has_feature(cxx_delegating_constructors)
 #      define Q_COMPILER_DELEGATING_CONSTRUCTORS
+#    endif
+#    if __has_feature(cxx_override_control)
 #      define Q_COMPILER_EXPLICIT_OVERRIDES
-#      define Q_COMPILER_NULLPTR
-#      define Q_COMPILER_RANGE_FOR
-#      define Q_COMPILER_UNICODE_STRINGS
 #    endif
-        /* not implemented in clang yet */
-#    if __has_feature(cxx_constexpr)
-#      define Q_COMPILER_CONSTEXPR
+#    if __has_feature(cxx_inheriting_constructors)
+#      define Q_COMPILER_INHERITING_CONSTRUCTORS
+#    endif
+#    if __has_feature(cxx_generalized_initializers)
+#      define Q_COMPILER_INITIALIZER_LISTS
 #    endif
 #    if __has_feature(cxx_lambdas)
 #      define Q_COMPILER_LAMBDA
 #    endif
-#    if __has_feature(cxx_generalized_initializers)
-#      define Q_COMPILER_INITIALIZER_LISTS
+#    if __has_feature(cxx_nonstatic_member_init)
+#      define Q_COMPILER_NONSTATIC_MEMBER_INIT
+#    endif
+#    if __has_feature(cxx_nullptr)
+#      define Q_COMPILER_NULLPTR
+#    endif
+#    if __has_feature(cxx_range_for)
+#      define Q_COMPILER_RANGE_FOR
+#    endif
+#    if __has_feature(cxx_raw_string_literals)
+#      define Q_COMPILER_RAW_STRINGS
+#    endif
+#    if __has_feature(cxx_reference_qualified_functions)
+#      define Q_COMPILER_REF_QUALIFIERS
+#    endif
+#    if __has_feature(cxx_rvalue_references)
+#      define Q_COMPILER_RVALUE_REFS
+#    endif
+#    if __has_feature(cxx_static_assert)
+#      define Q_COMPILER_STATIC_ASSERT
+#    endif
+#    if __has_feature(cxx_alias_templates)
+#      define Q_COMPILER_TEMPLATE_ALIAS
+#    endif
+#    if 0 /* not implemented in clang yet */
+#      define Q_COMPILER_THREAD_LOCAL
+#    endif
+#    if __has_feature(cxx_user_literals)
+#      define Q_COMPILER_UDL
+#    endif
+#    if __has_feature(cxx_unicode_literals)
+#      define Q_COMPILER_UNICODE_STRINGS
 #    endif
 #    if __has_feature(cxx_unrestricted_unions)
 #      define Q_COMPILER_UNRESTRICTED_UNIONS
 #    endif
-#    if 0
-#      define Q_COMPILER_ATOMICS
+#    if __has_feature(cxx_variadic_templates)
+#      define Q_COMPILER_VARIADIC_TEMPLATES
+#    endif
+    /* Features that have no __has_feature() check */
+#    if ((__clang_major__ * 100) + __clang_minor__) >= 209 /* since clang 2.9 */
+#      define Q_COMPILER_EXTERN_TEMPLATES
+#      define Q_COMPILER_VARIADIC_MACROS
 #    endif
 #  endif
 #endif // Q_CC_CLANG