Don't wrap feature detection macros with QT_HAS_FOO() variants

Using wrappers for these macros is problematic when for example passing the
-frewrite-includes flag to preprocess sources before shipping off to distcc
or Icecream. It will also start producing warnings when compilers implement
http://eel.is/c++draft/cpp.cond#7.sentence-2. See for example
https://reviews.llvm.org/D49091

Both https://clang.llvm.org/docs/LanguageExtensions.html and the SD-6 document at
https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations
recommend defining '__has_foo(x) 0' as a fallback for compilers without the
macros, so that's what we go for.

Change-Id: I0298cd3b4a6ff6618821e34642a5ddd6728be767
Reviewed-by: Alex Richardson <arichardson.kde@gmail.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/global/qcompilerdetection.h

@@ -505,6 +505,39 @@
 #  error "Qt has not been tested with this compiler - see http://www.qt-project.org/"
 #endif
 
+/*
+ * SG10's SD-6 feature detection and some useful extensions from Clang and GCC
+ * https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations
+ * http://clang.llvm.org/docs/LanguageExtensions.html#feature-checking-macros
+ * Not using wrapper macros, per http://eel.is/c++draft/cpp.cond#7.sentence-2
+ */
+#ifndef __has_builtin
+#  define __has_builtin(x)             0
+#endif
+#ifndef __has_feature
+#  define __has_feature(x)             0
+#endif
+#ifndef __has_attribute
+#  define __has_attribute(x)           0
+#endif
+#ifndef __has_cpp_attribute
+#  define __has_cpp_attribute(x)       0
+#endif
+#ifndef __has_include
+#  define __has_include(x)             0
+#endif
+#ifndef __has_include_next
+#  define __has_include_next(x)        0
+#endif
+
+// Kept around until all submodules have transitioned
+#define QT_HAS_BUILTIN(x)        __has_builtin(x)
+#define QT_HAS_FEATURE(x)        __has_feature(x)
+#define QT_HAS_ATTRIBUTE(x)      __has_attribute(x)
+#define QT_HAS_CPP_ATTRIBUTE(x)  __has_cpp_attribute(x)
+#define QT_HAS_INCLUDE(x)        __has_include(x)
+#define QT_HAS_INCLUDE_NEXT(x)   __has_include_next(x)
+
 /*
  * C++11 support
  *
@@ -1031,37 +1064,6 @@
 # endif
 #endif
 
-/*
- * SG10's SD-6 feature detection and some useful extensions from Clang and GCC
- * https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations
- * http://clang.llvm.org/docs/LanguageExtensions.html#feature-checking-macros
- */
-#ifdef __has_builtin
-#  define QT_HAS_BUILTIN(x)             __has_builtin(x)
-#else
-#  define QT_HAS_BUILTIN(x)             0
-#endif
-#ifdef __has_attribute
-#  define QT_HAS_ATTRIBUTE(x)           __has_attribute(x)
-#else
-#  define QT_HAS_ATTRIBUTE(x)           0
-#endif
-#ifdef __has_cpp_attribute
-#  define QT_HAS_CPP_ATTRIBUTE(x)       __has_cpp_attribute(x)
-#else
-#  define QT_HAS_CPP_ATTRIBUTE(x)       0
-#endif
-#ifdef __has_include
-#  define QT_HAS_INCLUDE(x)             __has_include(x)
-#else
-#  define QT_HAS_INCLUDE(x)             0
-#endif
-#ifdef __has_include_next
-#  define QT_HAS_INCLUDE_NEXT(x)        __has_include_next(x)
-#else
-#  define QT_HAS_INCLUDE_NEXT(x)        0
-#endif
-
 /*
  * C++11 keywords and expressions
  */
@@ -1138,7 +1140,7 @@
 #  define Q_DECL_ALIGN(n)   alignas(n)
 #endif
 
-#if QT_HAS_CPP_ATTRIBUTE(nodiscard) && !defined(Q_CC_CLANG)         // P0188R1
+#if __has_cpp_attribute(nodiscard) && !defined(Q_CC_CLANG)         // P0188R1
 // Can't use [[nodiscard]] with Clang, see https://bugs.llvm.org/show_bug.cgi?id=33518
 #  undef Q_REQUIRED_RESULT
 #  define Q_REQUIRED_RESULT [[nodiscard]]
@@ -1240,11 +1242,6 @@
 #ifndef QT_MAKE_CHECKED_ARRAY_ITERATOR
 #  define QT_MAKE_CHECKED_ARRAY_ITERATOR(x, N) (x)
 #endif
-#ifdef __has_feature
-#  define QT_HAS_FEATURE(x)             __has_feature(x)
-#else
-#  define QT_HAS_FEATURE(x)             0
-#endif
 
 /*
  * Warning/diagnostic handling
@@ -1335,11 +1332,11 @@
     } while (false)
 
 #if defined(__cplusplus)
-#if QT_HAS_CPP_ATTRIBUTE(clang::fallthrough)
+#if __has_cpp_attribute(clang::fallthrough)
 #    define Q_FALLTHROUGH() [[clang::fallthrough]]
-#elif QT_HAS_CPP_ATTRIBUTE(gnu::fallthrough)
+#elif __has_cpp_attribute(gnu::fallthrough)
 #    define Q_FALLTHROUGH() [[gnu::fallthrough]]
-#elif QT_HAS_CPP_ATTRIBUTE(fallthrough)
+#elif __has_cpp_attribute(fallthrough)
 #  define Q_FALLTHROUGH() [[fallthrough]]
 #endif
 #endif

src/corelib/global/qconfig-bootstrapped.h

@@ -75,13 +75,13 @@
 # define QT_FEATURE_alloca_malloc_h -1
 #endif
 #define QT_CRYPTOGRAPHICHASH_ONLY_SHA1
-#define QT_FEATURE_cxx11_random (QT_HAS_INCLUDE(<random>) ? 1 : -1)
+#define QT_FEATURE_cxx11_random (__has_include(<random>) ? 1 : -1)
 #define QT_NO_DATASTREAM
 #define QT_FEATURE_datestring 1
 #define QT_FEATURE_datetimeparser -1
 #define QT_FEATURE_easingcurve -1
 #define QT_FEATURE_etw -1
-#define QT_FEATURE_getauxval (QT_HAS_INCLUDE(<sys/auxv.h>) ? 1 : -1)
+#define QT_FEATURE_getauxval (__has_include(<sys/auxv.h>) ? 1 : -1)
 #define QT_FEATURE_getentropy -1
 #define QT_NO_GEOM_VARIANT
 #define QT_FEATURE_hijricalendar -1

src/corelib/global/qendian.h

@@ -66,7 +66,7 @@ template <typename T> Q_ALWAYS_INLINE void qToUnaligned(const T src, void *dest)
     // Using sizeof(T) inside memcpy function produces internal compiler error with
     // MSVC2008/ARM in tst_endian -> use extra indirection to resolve size of T.
     const size_t size = sizeof(T);
-#if QT_HAS_BUILTIN(__builtin_memcpy)
+#if __has_builtin(__builtin_memcpy)
     __builtin_memcpy
 #else
     memcpy
@@ -78,7 +78,7 @@ template <typename T> Q_ALWAYS_INLINE T qFromUnaligned(const void *src)
 {
     T dest;
     const size_t size = sizeof(T);
-#if QT_HAS_BUILTIN(__builtin_memcpy)
+#if __has_builtin(__builtin_memcpy)
     __builtin_memcpy
 #else
     memcpy

src/corelib/global/qglobal.cpp

@@ -92,7 +92,7 @@
 #  include <sys/systeminfo.h>
 #endif
 
-#if defined(Q_OS_DARWIN) && QT_HAS_INCLUDE(<IOKit/IOKitLib.h>)
+#if defined(Q_OS_DARWIN) && __has_include(<IOKit/IOKitLib.h>)
 #  include <IOKit/IOKitLib.h>
 #  include <private/qcore_mac_p.h>
 #endif
@@ -3041,7 +3041,7 @@ enum {
 */
 QByteArray QSysInfo::machineUniqueId()
 {
-#if defined(Q_OS_DARWIN) && QT_HAS_INCLUDE(<IOKit/IOKitLib.h>)
+#if defined(Q_OS_DARWIN) && __has_include(<IOKit/IOKitLib.h>)
     char uuid[UuidStringLen + 1];
     io_service_t service = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("IOPlatformExpertDevice"));
     QCFString stringRef = (CFStringRef)IORegistryEntryCreateCFProperty(service, CFSTR(kIOPlatformUUIDKey), kCFAllocatorDefault, 0);

src/corelib/global/qglobal.h

@@ -769,7 +769,7 @@ inline void qt_noop(void) {}
 
 #if !defined(QT_NO_EXCEPTIONS)
 #  if !defined(Q_MOC_RUN)
-#    if (defined(Q_CC_CLANG) && !defined(Q_CC_INTEL) && !QT_HAS_FEATURE(cxx_exceptions)) || \
+#    if (defined(Q_CC_CLANG) && !defined(Q_CC_INTEL) && !__has_feature(cxx_exceptions)) || \
         (defined(Q_CC_GNU) && !defined(__EXCEPTIONS))
 #      define QT_NO_EXCEPTIONS
 #    endif

src/corelib/global/qglobal_p.h

@@ -74,7 +74,7 @@ Q_CORE_EXPORT time_t qMkTime(struct tm *when);
 
 QT_END_NAMESPACE
 
-#if !QT_HAS_BUILTIN(__builtin_available)
+#if !__has_builtin(__builtin_available)
 #include <initializer_list>
 #include <QtCore/qoperatingsystemversion.h>
 #include <QtCore/qversionnumber.h>
@@ -142,7 +142,7 @@ QT_END_NAMESPACE
     QT_BUILTIN_AVAILABLE1, \
     QT_BUILTIN_AVAILABLE0, )
 #define __builtin_available(...) QT_BUILTIN_AVAILABLE_CHOOSER(__VA_ARGS__)(__VA_ARGS__)
-#endif // !QT_HAS_BUILTIN(__builtin_available)
+#endif // !__has_builtin(__builtin_available)
 #endif // defined(__cplusplus)
 
 #endif // QGLOBAL_P_H

src/corelib/global/qlogging.cpp

@@ -70,7 +70,7 @@
 #if QT_CONFIG(slog2)
 #include <sys/slog2.h>
 #endif
-#if QT_HAS_INCLUDE(<paths.h>)
+#if __has_include(<paths.h>)
 #include <paths.h>
 #endif
 
@@ -106,7 +106,7 @@
 #    if __UCLIBC_HAS_BACKTRACE__
 #      define QLOGGING_HAVE_BACKTRACE
 #    endif
-#  elif (defined(__GLIBC__) && defined(__GLIBCXX__)) || (QT_HAS_INCLUDE(<cxxabi.h>) && QT_HAS_INCLUDE(<execinfo.h>))
+#  elif (defined(__GLIBC__) && defined(__GLIBCXX__)) || (__has_include(<cxxabi.h>) && __has_include(<execinfo.h>))
 #    define QLOGGING_HAVE_BACKTRACE
 #  endif
 #endif
@@ -116,7 +116,7 @@ extern char *__progname;
 #endif
 
 #ifndef QT_BOOTSTRAPPED
-#if defined(Q_OS_LINUX) && (defined(__GLIBC__) || QT_HAS_INCLUDE(<sys/syscall.h>))
+#if defined(Q_OS_LINUX) && (defined(__GLIBC__) || __has_include(<sys/syscall.h>))
 #  include <sys/syscall.h>
 
 # if defined(Q_OS_ANDROID) && !defined(SYS_gettid)
@@ -1276,7 +1276,7 @@ void QMessagePattern::setPattern(const QString &pattern)
 #if defined(QLOGGING_HAVE_BACKTRACE) && !defined(QT_BOOTSTRAPPED)
 // make sure the function has "Message" in the name so the function is removed
 
-#if ((defined(Q_CC_GNU) && defined(QT_COMPILER_SUPPORTS_SIMD_ALWAYS)) || QT_HAS_ATTRIBUTE(optimize)) \
+#if ((defined(Q_CC_GNU) && defined(QT_COMPILER_SUPPORTS_SIMD_ALWAYS)) || __has_attribute(optimize)) \
     && !defined(Q_CC_INTEL) && !defined(Q_CC_CLANG)
 // force skipping the frame pointer, to save the backtrace() function some work
 __attribute__((optimize("omit-frame-pointer")))

src/corelib/global/qnumeric_p.h

@@ -249,7 +249,7 @@ QT_WARNING_POP
 // size_t. Implementations for 8- and 16-bit types will work but may not be as
 // efficient. Implementations for 64-bit may be missing on 32-bit platforms.
 
-#if (defined(Q_CC_GNU) && (Q_CC_GNU >= 500) || (defined(Q_CC_INTEL) && !defined(Q_OS_WIN))) || QT_HAS_BUILTIN(__builtin_add_overflow)
+#if (defined(Q_CC_GNU) && (Q_CC_GNU >= 500) || (defined(Q_CC_INTEL) && !defined(Q_OS_WIN))) || __has_builtin(__builtin_add_overflow)
 // GCC 5, ICC 18, and Clang 3.8 have builtins to detect overflows
 
 template <typename T> inline

src/corelib/io/qfilesystemengine_unix.cpp

@@ -55,7 +55,7 @@
 #include <stdio.h>
 #include <errno.h>
 
-#if QT_HAS_INCLUDE(<paths.h>)
+#if __has_include(<paths.h>)
 # include <paths.h>
 #endif
 #ifndef _PATH_TMP           // from <paths.h>

src/corelib/io/qprocess.cpp

@@ -100,7 +100,7 @@ QT_END_NAMESPACE
 #include <private/qcore_unix_p.h>
 #endif
 
-#if QT_HAS_INCLUDE(<paths.h>)
+#if __has_include(<paths.h>)
 #include <paths.h>
 #endif
 

src/corelib/io/qstandardpaths.cpp

@@ -48,7 +48,7 @@
 #include <qcoreapplication.h>
 #endif
 
-#if QT_HAS_INCLUDE(<paths.h>)
+#if __has_include(<paths.h>)
 #include <paths.h>
 #endif
 

src/corelib/io/qstorageinfo_unix.cpp

@@ -108,7 +108,7 @@
 #  endif // QT_LARGEFILE_SUPPORT
 #endif // Q_OS_BSD4
 
-#if QT_HAS_INCLUDE(<paths.h>)
+#if __has_include(<paths.h>)
 #  include <paths.h>
 #endif
 #ifndef _PATH_MOUNTED

src/corelib/kernel/qdeadlinetimer.h

@@ -52,7 +52,7 @@
 
 #include <limits>
 
-#if QT_HAS_INCLUDE(<chrono>)
+#if __has_include(<chrono>)
 #  include <chrono>
 #endif
 
@@ -120,7 +120,7 @@ class Q_CORE_EXPORT QDeadlineTimer
     QDeadlineTimer &operator-=(qint64 msecs)
     { *this = *this + (-msecs); return *this; }
 
-#if QT_HAS_INCLUDE(<chrono>) || defined(Q_CLANG_QDOC)
+#if __has_include(<chrono>) || defined(Q_CLANG_QDOC)
     template <class Clock, class Duration>
     QDeadlineTimer(std::chrono::time_point<Clock, Duration> deadline_,
                    Qt::TimerType type_ = Qt::CoarseTimer) : t2(0)

src/corelib/kernel/qobject.h

@@ -55,7 +55,7 @@
 
 #include <QtCore/qobject_impl.h>
 
-#if QT_HAS_INCLUDE(<chrono>)
+#if __has_include(<chrono>)
 #  include <chrono>
 #endif
 
@@ -160,7 +160,7 @@ class Q_CORE_EXPORT QObject
     void moveToThread(QThread *thread);
 
     int startTimer(int interval, Qt::TimerType timerType = Qt::CoarseTimer);
-#if QT_HAS_INCLUDE(<chrono>)
+#if __has_include(<chrono>)
     Q_ALWAYS_INLINE
     int startTimer(std::chrono::milliseconds time, Qt::TimerType timerType = Qt::CoarseTimer)
     {

src/corelib/kernel/qtimer.h

@@ -47,7 +47,7 @@
 #include <QtCore/qbasictimer.h> // conceptual inheritance
 #include <QtCore/qobject.h>
 
-#if QT_HAS_INCLUDE(<chrono>)
+#if __has_include(<chrono>)
 #  include <chrono>
 #endif
 
@@ -177,7 +177,7 @@ public Q_SLOTS:
     void timeout(QPrivateSignal);
 
 public:
-#if QT_HAS_INCLUDE(<chrono>) || defined(Q_QDOC)
+#if __has_include(<chrono>) || defined(Q_QDOC)
     void setInterval(std::chrono::milliseconds value)
     {
         setInterval(int(value.count()));
@@ -223,7 +223,7 @@ public Q_SLOTS:
     static void singleShotImpl(int msec, Qt::TimerType timerType,
                                const QObject *receiver, QtPrivate::QSlotObjectBase *slotObj);
 
-#if QT_HAS_INCLUDE(<chrono>)
+#if __has_include(<chrono>)
     static Qt::TimerType defaultTypeFor(std::chrono::milliseconds interval)
     { return defaultTypeFor(int(interval.count())); }
 

src/corelib/kernel/qvariant.h

@@ -53,7 +53,7 @@
 #include <QtCore/qbytearraylist.h>
 #endif
 
-#if QT_HAS_INCLUDE(<variant>) && __cplusplus >= 201703L
+#if __has_include(<variant>) && __cplusplus >= 201703L
 #include <variant>
 #elif defined(Q_CLANG_QDOC)
 namespace std { template<typename...> struct variant; }
@@ -370,7 +370,7 @@ class Q_CORE_EXPORT QVariant
     static inline QVariant fromValue(const T &value)
     { return QVariant(qMetaTypeId<T>(), &value, QTypeInfo<T>::isPointer); }
 
-#if (QT_HAS_INCLUDE(<variant>) && __cplusplus >= 201703L) || defined(Q_CLANG_QDOC)
+#if (__has_include(<variant>) && __cplusplus >= 201703L) || defined(Q_CLANG_QDOC)
     template<typename... Types>
     static inline QVariant fromStdVariant(const std::variant<Types...> &value)
     {
@@ -544,7 +544,7 @@ inline QVariant QVariant::fromValue(const QVariant &value)
     return value;
 }
 
-#if QT_HAS_INCLUDE(<variant>) && __cplusplus >= 201703L
+#if __has_include(<variant>) && __cplusplus >= 201703L
 template<>
 inline QVariant QVariant::fromValue(const std::monostate &)
 {

src/corelib/serialization/qcborarray.h

@@ -214,7 +214,7 @@ class Q_CORE_EXPORT QCborArray
     bool contains(const QCborValue &value) const;
 
     int compare(const QCborArray &other) const noexcept Q_DECL_PURE_FUNCTION;
-#if 0 && QT_HAS_INCLUDE(<compare>)
+#if 0 && __has_include(<compare>)
     std::strong_ordering operator<=>(const QCborArray &other) const
     {
         int c = compare(other);

src/corelib/serialization/qcbormap.h

@@ -245,7 +245,7 @@ class Q_CORE_EXPORT QCborMap
     { const_iterator it = find(key); return it != end(); }
 
     int compare(const QCborMap &other) const noexcept Q_DECL_PURE_FUNCTION;
-#if 0 && QT_HAS_INCLUDE(<compare>)
+#if 0 && __has_include(<compare>)
     std::strong_ordering operator<=>(const QCborMap &other) const
     {
         int c = compare(other);