CppTools: Fix MSVC toolchain flags for C-files

In case of C-header or C-source files the MSVC
language version was not switched to C.
Fixes static analyzer runs for C files.

Task-number: QTCREATORBUG-20198
Change-Id: I1da31a1048b7c258642cf00f5084681f5d384ee6
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cpptools/compileroptionsbuilder.cpp

@@ -47,6 +47,7 @@ CompilerOptionsBuilder::CompilerOptionsBuilder(const ProjectPart &projectPart,
     : m_projectPart(projectPart)
     , m_clangVersion(clangVersion)
     , m_clangResourceDirectory(clangResourceDirectory)
+    , m_languageVersion(m_projectPart.languageVersion)
 {
 }
 
@@ -54,6 +55,9 @@ QStringList CompilerOptionsBuilder::build(CppTools::ProjectFile::Kind fileKind,
 {
     m_options.clear();
 
+    if (fileKind == ProjectFile::CHeader || fileKind == ProjectFile::CSource)
+        QTC_ASSERT(m_languageVersion <= ProjectPart::LatestCVersion, return QStringList(););
+
     addWordWidth();
     addTargetTriple();
     addExtraCodeModelFlags();
@@ -119,7 +123,8 @@ void CompilerOptionsBuilder::addExtraCodeModelFlags()
 
 void CompilerOptionsBuilder::enableExceptions()
 {
-    add(QLatin1String("-fcxx-exceptions"));
+    if (m_languageVersion > ProjectPart::LatestCVersion)
+        add(QLatin1String("-fcxx-exceptions"));
     add(QLatin1String("-fexceptions"));
 }
 
@@ -287,7 +292,8 @@ void CompilerOptionsBuilder::addOptionsForLanguage(bool checkForBorlandExtension
     QStringList opts;
     const ProjectPart::LanguageExtensions languageExtensions = m_projectPart.languageExtensions;
     const bool gnuExtensions = languageExtensions & ProjectPart::GnuExtensions;
-    switch (m_projectPart.languageVersion) {
+
+    switch (m_languageVersion) {
     case ProjectPart::C89:
         opts << (gnuExtensions ? QLatin1String("-std=gnu89") : QLatin1String("-std=c89"));
         break;
@@ -472,9 +478,7 @@ QString CompilerOptionsBuilder::includeOption() const
 
 bool CompilerOptionsBuilder::excludeDefineDirective(const ProjectExplorer::Macro &macro) const
 {
-    // This is a quick fix for QTCREATORBUG-11501.
+    if (macro.key == "__cplusplus" && m_languageVersion <= ProjectPart::LatestCVersion)
-    // TODO: do a proper fix, see QTCREATORBUG-11709.
-    if (macro.key == "__cplusplus")
         return true;
 
     // Ignore for all compiler toolchains since LLVM has it's own implementation for

src/plugins/cpptools/compileroptionsbuilder.h

@@ -96,6 +96,7 @@ private:
     QStringList m_options;
     QString m_clangVersion;
     QString m_clangResourceDirectory;
+    ProjectPart::LanguageVersion m_languageVersion;
 };
 
 template<class T>

src/plugins/projectexplorer/abstractmsvctoolchain.cpp

@@ -133,15 +133,27 @@ ToolChain::CompilerFlags AbstractMsvcToolChain::compilerFlags(const QStringList
     if (cxxflags.contains(QLatin1String("/Za")))
         flags &= ~MicrosoftExtensions;
 
+    bool cLanguage = (language() == ProjectExplorer::Constants::C_LANGUAGE_ID);
+
     switch (m_abi.osFlavor()) {
     case Abi::WindowsMsvc2010Flavor:
-    case Abi::WindowsMsvc2012Flavor: flags |= StandardCxx11;
+    case Abi::WindowsMsvc2012Flavor:
+        if (cLanguage)
+            flags |= StandardC99;
+        else
+            flags |= StandardCxx11;
         break;
     case Abi::WindowsMsvc2013Flavor:
-    case Abi::WindowsMsvc2015Flavor: flags |= StandardCxx14;
+    case Abi::WindowsMsvc2015Flavor:
+        if (cLanguage)
+            flags |= StandardC99;
+        else
+            flags |= StandardCxx14;
         break;
     case Abi::WindowsMsvc2017Flavor:
-        if (cxxflags.contains("/std:c++17") || cxxflags.contains("/std:c++latest"))
+        if (cLanguage)
+            flags |= StandardC11;
+        else if (cxxflags.contains("/std:c++17") || cxxflags.contains("/std:c++latest"))
             flags |= StandardCxx17;
         else
             flags |= StandardCxx14;