CMake: remove tests for C++17 and C11 and earlier

Qt requires them and will fail to build if it isn't met, so we don't
need to check for its support. These were public CMake and qmake
features, so to keep compatibility with existing they're hardcoded now
(only done for the C++ editions and for qmake only, as that's what Qt 5
did).

Change-Id: I7f354474adce419ca6c2fffd174814724f45f90b
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

configure.cmake

@@ -204,51 +204,6 @@ endif()
 # machineTuple
 qt_config_compile_test_machine_tuple("machine tuple")
 
-# cxx14
-qt_config_compile_test(cxx14
-    LABEL "C++14 support"
-    CODE
-"#if __cplusplus > 201103L
-// Compiler claims to support C++14, trust it
-#else
-#  error __cplusplus must be > 201103L (the value of C++11)
-#endif
-
-int main(void)
-{
-    /* BEGIN TEST: */
-    /* END TEST: */
-    return 0;
-}
-"
-    CXX_STANDARD 14
-)
-
-# cxx17
-qt_config_compile_test(cxx17
-    LABEL "C++17 support"
-    CODE
-"#if __cplusplus > 201402L
-// Compiler claims to support C++17, trust it
-#else
-#  error __cplusplus must be > 201402L (the value for C++14)
-#endif
-#include <map>  // https://bugs.llvm.org//show_bug.cgi?id=33117
-#include <variant>
-
-int main(void)
-{
-    /* BEGIN TEST: */
-std::variant<int> v(42);
-int i = std::get<int>(v);
-std::visit([](const auto &) { return 1; }, v);
-    /* END TEST: */
-    return 0;
-}
-"
-    CXX_STANDARD 17
-)
-
 # cxx20
 qt_config_compile_test(cxx20
     LABEL "C++20 support"
@@ -660,29 +615,10 @@ qt_feature_config("plugin-manifests" QMAKE_PUBLIC_CONFIG
     NEGATE
     NAME "no_plugin_manifest"
 )
-qt_feature("c++11" PUBLIC
-    LABEL "C++11"
-)
-qt_feature_config("c++11" QMAKE_PUBLIC_QT_CONFIG)
-qt_feature("c++14" PUBLIC
-    LABEL "C++14"
-    CONDITION QT_FEATURE_cxx11 AND TEST_cxx14
-)
-qt_feature_config("c++14" QMAKE_PUBLIC_QT_CONFIG)
-qt_feature("c++17" PUBLIC
-    LABEL "C++17"
-    CONDITION QT_FEATURE_cxx14 AND TEST_cxx17
-)
-qt_feature_config("c++17" QMAKE_PUBLIC_QT_CONFIG)
-qt_feature("c++1z" PUBLIC
-    LABEL "C++17"
-    CONDITION QT_FEATURE_cxx17
-)
-qt_feature_config("c++1z" QMAKE_PUBLIC_QT_CONFIG)
 qt_feature("c++20" PUBLIC
     LABEL "C++20"
     AUTODETECT OFF
-    CONDITION QT_FEATURE_cxx17 AND TEST_cxx20
+    CONDITION TEST_cxx20
 )
 qt_feature_config("c++20" QMAKE_PUBLIC_QT_CONFIG)
 qt_feature("c++2a" PUBLIC
@@ -700,17 +636,6 @@ qt_feature("c++2b" PUBLIC
     AUTODETECT FALSE
     CONDITION QT_FEATURE_cxx20 AND (CMAKE_VERSION VERSION_GREATER_EQUAL "3.20") AND TEST_cxx2b
 )
-qt_feature("c89"
-    LABEL "C89"
-)
-qt_feature("c99" PUBLIC
-    LABEL "C99"
-    CONDITION c_std_99 IN_LIST CMAKE_C_COMPILE_FEATURES
-)
-qt_feature("c11" PUBLIC
-    LABEL "C11"
-    CONDITION QT_FEATURE_c99 AND c_std_11 IN_LIST CMAKE_C_COMPILE_FEATURES
-)
 qt_feature("precompile_header"
     LABEL "Using precompiled headers"
     CONDITION BUILD_WITH_PCH AND TEST_precompile_header
@@ -1142,16 +1067,6 @@ qt_configure_add_summary_entry(
 )
 # special case end
 qt_configure_add_summary_entry(ARGS "shared")
-qt_configure_add_summary_entry(
-    TYPE "firstAvailableFeature"
-    ARGS "c11 c99 c89"
-    MESSAGE "Using C standard"
-)
-qt_configure_add_summary_entry(
-    TYPE "firstAvailableFeature"
-    ARGS "c++2b c++20 c++17 c++14 c++11"
-    MESSAGE "Using C++ standard"
-)
 qt_configure_add_summary_entry(
     ARGS "ccache"
     CONDITION UNIX

mkspecs/features/mac/default_post.prf

@@ -50,29 +50,6 @@ contains(TEMPLATE, .*app) {
 
 !no_objective_c:CONFIG += objective_c
 
-qt {
-    qtConfig(static) {
-        # C++11 support means using libc++ instead of libstd++. As the
-        # two libraries are incompatible we need to ensure the end user
-        # project is built using the same C++11 support/no support as Qt.
-        qtConfig(c++11) {
-            CONFIG += c++11
-        } else: c++11 {
-            warning("Qt was not built with C++11 enabled, disabling feature")
-            CONFIG -= c++11
-        }
-
-        !c++11 {
-            # Explicitly use libstdc++ if C++11 support is not enabled,
-            # as otherwise the compiler will choose the standard library
-            # based on the deployment target, which for iOS 7 and OS X 10.9
-            # is libc++, and we can't mix and match the two.
-            QMAKE_CXXFLAGS += -stdlib=libstdc++
-            QMAKE_LFLAGS   += -stdlib=libstdc++
-        }
-    }
-}
-
 # Add the same default rpaths as Xcode does for new projects.
 # This is especially important for iOS/tvOS/watchOS where no other option is possible.
 !no_default_rpath {

mkspecs/features/qt.prf

@@ -2,6 +2,9 @@
 # due to required Qt modules being missing.
 !isEmpty(QMAKE_FAILED_REQUIREMENTS): return()
 
+# hardcoded defaults
+QT_CONFIG *= c99 c11 c++11 c++14 c++1z c++17
+
 qtConfig(thread): CONFIG *= thread
 
 #handle defines