try_compile: Tolerate compile features from non-enabled languages

Do not copy the list of enabled languages from the outer generator.
It is populated as languages are enabled inside the test project.

Fixes: #27684

Source/cmGlobalGenerator.cxx

@@ -2573,8 +2573,7 @@ std::unique_ptr<cmLocalGenerator> cmGlobalGenerator::CreateLocalGenerator(
   return cm::make_unique<cmLocalGenerator>(this, mf);
 }
 
-void cmGlobalGenerator::EnableLanguagesFromGenerator(cmGlobalGenerator* gen,
-                                                     cmMakefile* mf)
+void cmGlobalGenerator::SetupTryCompile(cmGlobalGenerator* gen, cmMakefile* mf)
 {
   this->SetConfiguredFilesPath(gen);
   this->TryCompileOuterMakefile = mf;
@@ -2582,15 +2581,7 @@ void cmGlobalGenerator::EnableLanguagesFromGenerator(cmGlobalGenerator* gen,
     gen->GetCMakeInstance()->GetCacheDefinition("CMAKE_MAKE_PROGRAM");
   this->GetCMakeInstance()->AddCacheEntry(
     "CMAKE_MAKE_PROGRAM", make, "make program", cmStateEnums::FILEPATH);
-  // copy the enabled languages
-  this->GetCMakeInstance()->GetState()->SetEnabledLanguages(
-    gen->GetCMakeInstance()->GetState()->GetEnabledLanguages());
   this->LanguagesReadyForTryCompile = gen->LanguagesReadyForTryCompile;
-  this->ExtensionToLanguage = gen->ExtensionToLanguage;
-  this->IgnoreExtensions = gen->IgnoreExtensions;
-  this->LanguageToOutputExtension = gen->LanguageToOutputExtension;
-  this->LanguageToLinkerPreference = gen->LanguageToLinkerPreference;
-  this->OutputExtensions = gen->OutputExtensions;
 }
 
 void cmGlobalGenerator::SetConfiguredFilesPath(cmGlobalGenerator* gen)

Source/cmGlobalGenerator.h

@@ -240,11 +240,7 @@ public:
   void ResolveLanguageCompiler(std::string const& lang, cmMakefile* mf,
                                bool optional) const;
 
-  /**
-   * Try to determine system information, get it from another generator
-   */
-  void EnableLanguagesFromGenerator(cmGlobalGenerator* gen, cmMakefile* mf);
-
+  void SetupTryCompile(cmGlobalGenerator* gen, cmMakefile* mf);
   /**
    * Try running cmake and building a file. This is used for dynamically
    * loaded commands, not as part of the usual build process.
@@ -870,8 +866,6 @@ private:
   std::map<cmGeneratorTarget const*, size_t> TargetOrderIndex;
 
   cmMakefile* TryCompileOuterMakefile;
-  // If you add a new map here, make sure it is copied
-  // in EnableLanguagesFromGenerator
   std::map<std::string, bool> IgnoreExtensions;
   std::set<std::string> LanguagesReadyForTryCompile;
   std::set<std::string> LanguagesInProgress;

Source/cmMakefile.cxx

@@ -3347,8 +3347,7 @@ int cmMakefile::TryCompile(std::string const& srcdir,
     cm.SetCacheArgs(*cmakeArgs);
   }
   // to save time we pass the EnableLanguage info directly
-  cm.GetGlobalGenerator()->EnableLanguagesFromGenerator(
-    this->GetGlobalGenerator(), this);
+  cm.GetGlobalGenerator()->SetupTryCompile(this->GetGlobalGenerator(), this);
   for (unsigned dc = 1; dc < cmDiagnostics::CategoryCount; ++dc) {
     auto const category = static_cast<cmDiagnosticCategory>(dc);
     if (this->GetDiagnosticAction(category) == cmDiagnostics::Ignore) {

Source/cmState.cxx

@@ -390,11 +390,6 @@ std::vector<std::string> cmState::GetEnabledLanguages() const
   return this->EnabledLanguages;
 }
 
-void cmState::SetEnabledLanguages(std::vector<std::string> const& langs)
-{
-  this->EnabledLanguages = langs;
-}
-
 void cmState::ClearEnabledLanguages()
 {
   this->EnabledLanguages.clear();

Source/cmState.h

@@ -159,7 +159,6 @@ public:
   void SetLanguageEnabled(std::string const& l);
   bool GetLanguageEnabled(std::string const& l) const;
   std::vector<std::string> GetEnabledLanguages() const;
-  void SetEnabledLanguages(std::vector<std::string> const& langs);
   void ClearEnabledLanguages();
 
   bool GetIsGeneratorMultiConfig() const;

Tests/RunCMake/CheckSourceCompiles/MultipleLanguages.cmake

@@ -0,0 +1,11 @@
+enable_language (C CXX)
+include(CheckSourceCompiles)
+
+add_library(cxx_iface INTERFACE IMPORTED)
+target_compile_features(cxx_iface INTERFACE cxx_std_11)
+set(CMAKE_REQUIRED_LIBRARIES cxx_iface)
+
+check_source_compiles(C "int main() {return 0;}" SHOULD_BUILD)
+if(NOT SHOULD_BUILD)
+  message(SEND_ERROR "Test fail for valid C source.")
+endif()

Tests/RunCMake/CheckSourceCompiles/RunCMakeTest.cmake

@@ -3,6 +3,7 @@ include(RunCMake)
 run_cmake(NotEnabledLanguage)
 run_cmake(NonExistentLanguage)
 run_cmake(UnknownArgument)
+run_cmake(MultipleLanguages)
 
 run_cmake(CheckCSourceCompiles)
 run_cmake(CheckCXXSourceCompiles)