Remove checks for features available in C++17

This patch removes most of the checks that are made using C++20
__cpp_* macros for features available in C++17 and earlier.
Library feature check macros (__cpp_lib_*) are unaffected.

Change-Id: I557b2bd0d4ff09b13837555e9880eb28e0355f64
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

9 files changed, 2 insertions, 32 deletions

diff --git a/src/concurrent/qtconcurrentfunctionwrappers.h b/src/concurrent/qtconcurrentfunctionwrappers.h
index 1c882d3f19..08966115d6 100644
--- a/src/concurrent/qtconcurrentfunctionwrappers.h
+++ b/src/concurrent/qtconcurrentfunctionwrappers.h
@@ -129,7 +129,6 @@ struct ReduceResultType<R(*)(A...)>
     using ResultType = typename std::tuple_element<0, std::tuple<A...>>::type;
 };
 
-#if defined(__cpp_noexcept_function_type) && __cpp_noexcept_function_type >= 201510
 template <class U, class V>
 struct ReduceResultType<void(*)(U&,V) noexcept>
 {
@@ -141,7 +140,6 @@ struct ReduceResultType<T(C::*)(U) noexcept>
 {
     using ResultType = C;
 };
-#endif
 
 template<class T, class Enable = void>
 struct hasCallOperator : std::false_type
diff --git a/src/corelib/global/qcompilerdetection.h b/src/corelib/global/qcompilerdetection.h
index 273575c31f..bfa4f89105 100644
--- a/src/corelib/global/qcompilerdetection.h
+++ b/src/corelib/global/qcompilerdetection.h
@@ -1114,10 +1114,8 @@
 #  define Q_DECL_DEPRECATED_X(x) [[deprecated(x)]]
 #endif
 
-#if defined(__cpp_enumerator_attributes) && __cpp_enumerator_attributes >= 201411
-#  define Q_DECL_ENUMERATOR_DEPRECATED Q_DECL_DEPRECATED
-#  define Q_DECL_ENUMERATOR_DEPRECATED_X(x) Q_DECL_DEPRECATED_X(x)
-#endif
+#define Q_DECL_ENUMERATOR_DEPRECATED Q_DECL_DEPRECATED
+#define Q_DECL_ENUMERATOR_DEPRECATED_X(x) Q_DECL_DEPRECATED_X(x)
 
 /*
  * Fallback macros to certain compiler features
@@ -1153,12 +1151,6 @@
 #ifndef Q_DECL_DEPRECATED_X
 #  define Q_DECL_DEPRECATED_X(text) Q_DECL_DEPRECATED
 #endif
-#ifndef Q_DECL_ENUMERATOR_DEPRECATED
-#  define Q_DECL_ENUMERATOR_DEPRECATED
-#endif
-#ifndef Q_DECL_ENUMERATOR_DEPRECATED_X
-#  define Q_DECL_ENUMERATOR_DEPRECATED_X(x)
-#endif
 #ifndef Q_DECL_EXPORT
 #  define Q_DECL_EXPORT
 #endif
diff --git a/src/corelib/kernel/qobjectdefs_impl.h b/src/corelib/kernel/qobjectdefs_impl.h
index c35d9aa7a7..a3068e1712 100644
--- a/src/corelib/kernel/qobjectdefs_impl.h
+++ b/src/corelib/kernel/qobjectdefs_impl.h
@@ -158,7 +158,6 @@ namespace QtPrivate {
             (o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...), ApplyReturnValue<R>(arg[0]);
         }
     };
-#if defined(__cpp_noexcept_function_type) && __cpp_noexcept_function_type >= 201510
     template <int... II, typename... SignalArgs, typename R, typename... SlotArgs, typename SlotRet, class Obj>
     struct FunctorCall<IndexesList<II...>, List<SignalArgs...>, R, SlotRet (Obj::*)(SlotArgs...) noexcept> {
         static void call(SlotRet (Obj::*f)(SlotArgs...) noexcept, Obj *o, void **arg) {
@@ -171,7 +170,6 @@ namespace QtPrivate {
             (o->*f)((*reinterpret_cast<typename RemoveRef<SignalArgs>::Type *>(arg[II+1]))...), ApplyReturnValue<R>(arg[0]);
         }
     };
-#endif
 
     template<class Obj, typename Ret, typename... Args> struct FunctionPointer<Ret (Obj::*) (Args...)>
     {
@@ -210,7 +208,6 @@ namespace QtPrivate {
         }
     };
 
-#if defined(__cpp_noexcept_function_type) && __cpp_noexcept_function_type >= 201510
     template<class Obj, typename Ret, typename... Args> struct FunctionPointer<Ret (Obj::*) (Args...) noexcept>
     {
         typedef Obj Object;
@@ -247,7 +244,6 @@ namespace QtPrivate {
             FunctorCall<typename Indexes<ArgumentCount>::Value, SignalArgs, R, Function>::call(f, arg);
         }
     };
-#endif
 
     template<typename Function, int N> struct Functor
     {
diff --git a/src/corelib/thread/qlocking_p.h b/src/corelib/thread/qlocking_p.h
index 9a796cf7f7..5fb80454df 100644
--- a/src/corelib/thread/qlocking_p.h
+++ b/src/corelib/thread/qlocking_p.h
@@ -84,15 +84,11 @@ QT_BEGIN_NAMESPACE
 namespace {
 
 template <typename Mutex, typename Lock =
-#if defined(__cpp_guaranteed_copy_elision) && __cpp_guaranteed_copy_elision >= 201606L
 # if defined(__cpp_lib_scoped_lock) && __cpp_lib_scoped_lock >= 201703L
           std::scoped_lock
 # else
           std::lock_guard
 # endif
-#else
-          std::unique_lock
-#endif
           <typename std::decay<Mutex>::type>
 >
 Lock qt_scoped_lock(Mutex &mutex)
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 0329dd37da..07e5970faf 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -663,12 +663,10 @@ public:
     }
 };
 
-#if defined(__cpp_deduction_guides) && __cpp_deduction_guides >= 201606
 template <typename InputIterator,
           typename ValueType = typename std::iterator_traits<InputIterator>::value_type,
           QtPrivate::IfIsInputIterator<InputIterator> = true>
 QList(InputIterator, InputIterator) -> QList<ValueType>;
-#endif
 
 template <typename T>
 inline void QList<T>::resize_internal(qsizetype newSize)
diff --git a/src/corelib/tools/qscopeguard.h b/src/corelib/tools/qscopeguard.h
index 8270f41a2e..cc9e8db209 100644
--- a/src/corelib/tools/qscopeguard.h
+++ b/src/corelib/tools/qscopeguard.h
@@ -86,9 +86,7 @@ private:
     bool m_invoke = true;
 };
 
-#ifdef __cpp_deduction_guides
 template <typename F> QScopeGuard(F(&)()) -> QScopeGuard<F(*)()>;
-#endif
 
 //! [qScopeGuard]
 template <typename F>
diff --git a/src/corelib/tools/qset.h b/src/corelib/tools/qset.h
index 565b8b5691..9aecbff5bc 100644
--- a/src/corelib/tools/qset.h
+++ b/src/corelib/tools/qset.h
@@ -235,12 +235,10 @@ private:
     Hash q_hash;
 };
 
-#if defined(__cpp_deduction_guides) && __cpp_deduction_guides >= 201606
 template <typename InputIterator,
           typename ValueType = typename std::iterator_traits<InputIterator>::value_type,
           QtPrivate::IfIsInputIterator<InputIterator> = true>
 QSet(InputIterator, InputIterator) -> QSet<ValueType>;
-#endif
 
 template <typename T>
 size_t qHash(const QSet<T> &key, size_t seed = 0)
diff --git a/src/corelib/tools/qvarlengtharray.h b/src/corelib/tools/qvarlengtharray.h
index 3aa5e70114..90be3b3299 100644
--- a/src/corelib/tools/qvarlengtharray.h
+++ b/src/corelib/tools/qvarlengtharray.h
@@ -386,12 +386,10 @@ private:
     }
 };
 
-#if defined(__cpp_deduction_guides) && __cpp_deduction_guides >= 201606
 template <typename InputIterator,
           typename ValueType = typename std::iterator_traits<InputIterator>::value_type,
           QtPrivate::IfIsInputIterator<InputIterator> = true>
 QVarLengthArray(InputIterator, InputIterator) -> QVarLengthArray<ValueType>;
-#endif
 
 template <class T, qsizetype Prealloc>
 Q_INLINE_TEMPLATE QVarLengthArray<T, Prealloc>::QVarLengthArray(qsizetype asize)
diff --git a/src/gui/painting/qrgba64.h b/src/gui/painting/qrgba64.h
index 2c644c4cf0..e326c03bfc 100644
--- a/src/gui/painting/qrgba64.h
+++ b/src/gui/painting/qrgba64.h
@@ -118,7 +118,6 @@ public:
     constexpr quint8 alpha8() const { return div_257(alpha()); }
     constexpr uint toArgb32() const
     {
-#if defined(__cpp_constexpr) && __cpp_constexpr-0 >= 201304
         quint64 br = rgba & Q_UINT64_C(0xffff0000ffff);
         quint64 ag = (rgba >> 16) & Q_UINT64_C(0xffff0000ffff);
         br += Q_UINT64_C(0x8000000080);
@@ -136,9 +135,6 @@ public:
              | (ag         & 0xff00)
              | ((br >> 32) & 0xff);
 #endif
-#else
-        return uint((alpha8() << 24) | (red8() << 16) | (green8() << 8) | blue8());
-#endif
     }
     constexpr ushort toRgb16() const
     {