Remove checks for C++ standard versions C++17 and below

Qt requires a compiler that support C++17 thus __cplusplus
is always 201703L or higher. This patch removes checks
for __cplusplus value that always succeed.

Change-Id: I4b830683ecefab8f913d8b09604086d53209d2e3
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

examples/widgets/widgets/tetrix/tetrixwindow.cpp

@@ -89,21 +89,12 @@ TetrixWindow::TetrixWindow(QWidget *parent)
 //! [4] //! [5]
     connect(quitButton , &QPushButton::clicked, qApp, &QCoreApplication::quit);
     connect(pauseButton, &QPushButton::clicked, board, &TetrixBoard::pause);
-#if __cplusplus >= 201402L
     connect(board, &TetrixBoard::scoreChanged,
             scoreLcd, qOverload<int>(&QLCDNumber::display));
     connect(board, &TetrixBoard::levelChanged,
             levelLcd, qOverload<int>(&QLCDNumber::display));
     connect(board, &TetrixBoard::linesRemovedChanged,
             linesLcd, qOverload<int>(&QLCDNumber::display));
-#else
-    connect(board, &TetrixBoard::scoreChanged,
-            scoreLcd, QOverload<int>::of(&QLCDNumber::display));
-    connect(board, &TetrixBoard::levelChanged,
-            levelLcd, QOverload<int>::of(&QLCDNumber::display));
-    connect(board, &TetrixBoard::linesRemovedChanged,
-            linesLcd, QOverload<int>::of(&QLCDNumber::display));
-#endif
 //! [5]
 
 //! [6]

src/corelib/kernel/qproperty.h

@@ -56,7 +56,7 @@
 #endif
 #endif
 
-#if !defined(QT_PROPERTY_COLLECT_BINDING_LOCATION) && __has_include(<experimental/source_location>) && __cplusplus >= 201703L && !defined(Q_CLANG_QDOC)
+#if !defined(QT_PROPERTY_COLLECT_BINDING_LOCATION) && __has_include(<experimental/source_location>) && !defined(Q_CLANG_QDOC)
 #include <experimental/source_location>
 #if defined(__cpp_lib_experimental_source_location)
 #define QT_SOURCE_LOCATION_NAMESPACE std::experimental

src/corelib/kernel/qvariant.h

@@ -58,7 +58,7 @@
 #include <memory>
 #include <type_traits>
 
-#if __has_include(<variant>) && __cplusplus >= 201703L
+#if __has_include(<variant>)
 #include <variant>
 #elif defined(Q_CLANG_QDOC)
 namespace std { template<typename...> struct variant; }
@@ -402,7 +402,7 @@ class Q_CORE_EXPORT QVariant
         return QVariant(QMetaType::fromType<T>(), std::addressof(value));
     }
 
-#if (__has_include(<variant>) && __cplusplus >= 201703L) || defined(Q_CLANG_QDOC)
+#if __has_include(<variant>) || defined(Q_CLANG_QDOC)
     template<typename... Types>
     static inline QVariant fromStdVariant(const std::variant<Types...> &value)
     {
@@ -580,7 +580,7 @@ inline QVariant QVariant::fromValue(const QVariant &value)
     return value;
 }
 
-#if __has_include(<variant>) && __cplusplus >= 201703L
+#if __has_include(<variant>)
 template<>
 inline QVariant QVariant::fromValue(const std::monostate &)
 {

src/corelib/text/qstring.h

@@ -1466,12 +1466,7 @@ inline std::wstring QString::toStdWString() const
 {
     std::wstring str;
     str.resize(length());
-#if __cplusplus >= 201703L
     str.resize(toWCharArray(str.data()));
-#else
-    if (length())
-        str.resize(toWCharArray(&str.front()));
-#endif
     return str;
 }
 

src/corelib/text/qstringtokenizer.h

@@ -46,9 +46,7 @@ QT_BEGIN_NAMESPACE
 
 template <typename, typename> class QStringBuilder;
 
-#if defined(Q_QDOC) || 1 || (defined(__cpp_range_based_for) && __cpp_range_based_for >= 201603)
-#  define Q_STRINGTOKENIZER_USE_SENTINEL
-#endif
+#define Q_STRINGTOKENIZER_USE_SENTINEL
 
 class QStringTokenizerBaseBase
 {

src/corelib/tools/qduplicatetracker_p.h

@@ -52,7 +52,7 @@
 
 #include <qglobal.h>
 
-#if __has_include(<memory_resource>) && __cplusplus > 201402L
+#if __has_include(<memory_resource>)
 #  include <unordered_set>
 #  include <memory_resource>
 #  include <qhash.h> // for the hashing helpers

tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp

@@ -35,7 +35,7 @@
 #if __has_include(<source_location>) && __cplusplus >= 202002L && !defined(Q_CLANG_QDOC)
 #include <source_location>
 #define QT_SOURCE_LOCATION_NAMESPACE std
-#elif __has_include(<experimental/source_location>) && __cplusplus >= 201703L && !defined(Q_CLANG_QDOC)
+#elif __has_include(<experimental/source_location>) && !defined(Q_CLANG_QDOC)
 #include <experimental/source_location>
 #define QT_SOURCE_LOCATION_NAMESPACE std::experimental
 #endif

tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp

@@ -48,7 +48,7 @@
 #include <limits.h>
 #include <float.h>
 #include <cmath>
-#if __has_include(<variant>) && __cplusplus >= 201703L
+#if __has_include(<variant>)
 #include <variant>
 #endif
 #include <QRegularExpression>
@@ -4882,7 +4882,7 @@ void tst_QVariant::shouldDeleteVariantDataWorksForAssociative()
 
 void tst_QVariant::fromStdVariant()
 {
-#if __has_include(<variant>) && __cplusplus >= 201703L
+#if __has_include(<variant>)
     {
         typedef std::variant<int, bool> intorbool_t;
         intorbool_t stdvar = 5;

tests/benchmarks/corelib/thread/qreadwritelock/tst_bench_qreadwritelock.cpp

@@ -30,10 +30,8 @@
 #include <QTest>
 #include <mutex>
 #if __has_include(<shared_mutex>)
-#if __cplusplus > 201103L
 #include <shared_mutex>
 #endif
-#endif
 #include <vector>
 
 // Wrapers that take pointers instead of reference to have the same interface as Qt