qmake/vcxproj generator: Handle C standard compiler flags

Handle the compiler flags /std:c11 and /std:c17 and turn them into the
values stdc11 and stc17 for the LanguageStandard_C tag.

Drive-by change: Add /std:c++20 to the list of known C++ standard
options.

Task-number: QTBUG-89296
Change-Id: Ia575fff611bdf795406db84bd34057d008c8a383
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
(cherry picked from commit 5e98769602c1e7aa6ceeb45ffeee1680c58f4cda)

3 files changed, 36 insertions, 6 deletions

diff --git a/qmake/generators/win32/msbuild_objectmodel.cpp b/qmake/generators/win32/msbuild_objectmodel.cpp
index b5606309a8..fbd0a799dd 100644
--- a/qmake/generators/win32/msbuild_objectmodel.cpp
+++ b/qmake/generators/win32/msbuild_objectmodel.cpp
@@ -144,6 +144,7 @@ const char _IntermediateDirectory[]             = "IntermediateDirectory";
 const char _KeyContainer[]                      = "KeyContainer";
 const char _KeyFile[]                           = "KeyFile";
 const char _LanguageStandard[]                  = "LanguageStandard";
+const char _LanguageStandard_C[]                = "LanguageStandard_C";
 const char _LargeAddressAware[]                 = "LargeAddressAware";
 const char _LinkDLL[]                           = "LinkDLL";
 const char _LinkErrorReporting[]                = "LinkErrorReporting";
@@ -1483,6 +1484,7 @@ void VCXProjectWriter::write(XmlOutput &xml, const VCCLCompilerTool &tool)
             << attrTagT(_MinimalRebuild, tool.MinimalRebuild)
             << attrTagT(_MultiProcessorCompilation, tool.MultiProcessorCompilation)
             << attrTagS(_LanguageStandard, tool.LanguageStandard)
+            << attrTagS(_LanguageStandard_C, tool.LanguageStandard_C)
             << attrTagS(_ObjectFileName, tool.ObjectFile)
             << attrTagT(_OmitDefaultLibName, tool.OmitDefaultLibName)
             << attrTagT(_OmitFramePointers, tool.OmitFramePointers)
diff --git a/qmake/generators/win32/msvc_objectmodel.cpp b/qmake/generators/win32/msvc_objectmodel.cpp
index 7dc179823d..bd35f60630 100644
--- a/qmake/generators/win32/msvc_objectmodel.cpp
+++ b/qmake/generators/win32/msvc_objectmodel.cpp
@@ -1151,12 +1151,39 @@ bool VCCLCompilerTool::parseOption(const char* option)
             ShowIncludes = _True;
             break;
         }
-        if (strlen(option) > 8 && second == 't' && third == 'd') {
-            const QString version = option + 8;
-            static const QStringList knownVersions = { "14", "17", "latest" };
-            if (knownVersions.contains(version)) {
-                LanguageStandard = "stdcpp" + version;
-                break;
+        if (strlen(option) > 7 && second == 't' && third == 'd' && fourth == ':') {
+            static const QRegExp rex("(c(?:\\+\\+)?)(.+)");
+            if (rex.exactMatch(option + 5)) {
+                QString *var = nullptr;
+                const QStringList *knownVersions = nullptr;
+                QString valuePrefix;
+                auto lang = rex.cap(1);
+                auto version = rex.cap(2);
+                if (lang == QStringLiteral("c++")) {
+                    // Turn /std:c++17 into <LanguageStandard>stdcpp17</LanguageStandard>
+                    static const QStringList knownCxxVersions = {
+                        "14",
+                        "17",
+                        "20",
+                        "latest"
+                    };
+                    var = &LanguageStandard;
+                    knownVersions = &knownCxxVersions;
+                    valuePrefix = "stdcpp";
+                } else if (lang == QStringLiteral("c")) {
+                    // Turn /std:c17 into <LanguageStandard_C>stdc17</LanguageStandard_C>
+                    static const QStringList knownCVersions = {
+                        "11",
+                        "17"
+                    };
+                    var = &LanguageStandard_C;
+                    knownVersions = &knownCVersions;
+                    valuePrefix = "stdc";
+                }
+                if (var && knownVersions->contains(version)) {
+                    *var = valuePrefix + version;
+                    break;
+                }
             }
         }
         found = false; break;
diff --git a/qmake/generators/win32/msvc_objectmodel.h b/qmake/generators/win32/msvc_objectmodel.h
index 1e0c16bb45..c2259e8682 100644
--- a/qmake/generators/win32/msvc_objectmodel.h
+++ b/qmake/generators/win32/msvc_objectmodel.h
@@ -527,6 +527,7 @@ public:
     inlineExpansionOption   InlineFunctionExpansion;
     triState                KeepComments;
     QString                 LanguageStandard;
+    QString                 LanguageStandard_C;
     triState                MinimalRebuild;
     QString                 ObjectFile;
     triState                OmitDefaultLibName;