Move AddCompilerRequirementFlag to cmStandardLevelResolver

The cmLocalGenerator::AddCompilerRequirementFlag was another
source of truth on what standard levels existed per language,
so fold that into cmStandardLevelResolver to make updating
CMake easier

Source/cmLocalGenerator.cxx

@@ -2156,153 +2156,18 @@ void cmLocalGenerator::AddCompilerRequirementFlag(
   std::string& flags, cmGeneratorTarget const* target, const std::string& lang,
   const std::string& config)
 {
-  if (lang.empty()) {
-    return;
-  }
-  const char* defaultStd =
-    this->Makefile->GetDefinition("CMAKE_" + lang + "_STANDARD_DEFAULT");
-  if (!defaultStd || !*defaultStd) {
-    // This compiler has no notion of language standard levels.
-    return;
-  }
-  bool ext = true;
-  if (cmProp extPropValue = target->GetLanguageExtensions(lang)) {
-    if (cmIsOff(*extPropValue)) {
-      ext = false;
-    }
-  }
-  cmProp standardProp = target->GetLanguageStandard(lang, config);
-  if (!standardProp) {
-    if (ext) {
-      // No language standard is specified and extensions are not disabled.
-      // Check if this compiler needs a flag to enable extensions.
-      std::string const option_flag =
-        "CMAKE_" + lang + "_EXTENSION_COMPILE_OPTION";
-      if (const char* opt =
-            target->Target->GetMakefile()->GetDefinition(option_flag)) {
-        std::vector<std::string> optVec = cmExpandedList(opt);
-        for (std::string const& i : optVec) {
-          this->AppendFlagEscape(flags, i);
-        }
-      }
-    }
-    return;
-  }
+  cmStandardLevelResolver standardResolver(this->Makefile);
 
-  std::string const type = ext ? "EXTENSION" : "STANDARD";
-
-  if (target->GetLanguageStandardRequired(lang)) {
-    std::string option_flag =
-      "CMAKE_" + lang + *standardProp + "_" + type + "_COMPILE_OPTION";
-
-    const char* opt =
-      target->Target->GetMakefile()->GetDefinition(option_flag);
-    if (!opt) {
-      std::ostringstream e;
-      e << "Target \"" << target->GetName()
-        << "\" requires the language "
-           "dialect \""
-        << lang << *standardProp << "\" "
-        << (ext ? "(with compiler extensions)" : "")
-        << ", but CMake "
-           "does not know the compile flags to use to enable it.";
-      this->IssueMessage(MessageType::FATAL_ERROR, e.str());
-    } else {
+  std::string const& optionFlagDef =
+    standardResolver.GetCompileOptionDef(target, lang, config);
+  if (!optionFlagDef.empty()) {
+    auto opt = target->Target->GetMakefile()->GetDefinition(optionFlagDef);
+    if (opt) {
       std::vector<std::string> optVec = cmExpandedList(opt);
       for (std::string const& i : optVec) {
         this->AppendFlagEscape(flags, i);
       }
     }
-    return;
-  }
-
-  static std::map<std::string, std::vector<std::string>> langStdMap;
-  if (langStdMap.empty()) {
-    // Maintain sorted order, most recent first.
-    langStdMap["CXX"].emplace_back("20");
-    langStdMap["CXX"].emplace_back("17");
-    langStdMap["CXX"].emplace_back("14");
-    langStdMap["CXX"].emplace_back("11");
-    langStdMap["CXX"].emplace_back("98");
-
-    langStdMap["OBJCXX"].emplace_back("20");
-    langStdMap["OBJCXX"].emplace_back("17");
-    langStdMap["OBJCXX"].emplace_back("14");
-    langStdMap["OBJCXX"].emplace_back("11");
-    langStdMap["OBJCXX"].emplace_back("98");
-
-    langStdMap["C"].emplace_back("11");
-    langStdMap["C"].emplace_back("99");
-    langStdMap["C"].emplace_back("90");
-
-    langStdMap["OBJC"].emplace_back("11");
-    langStdMap["OBJC"].emplace_back("99");
-    langStdMap["OBJC"].emplace_back("90");
-
-    langStdMap["CUDA"].emplace_back("20");
-    langStdMap["CUDA"].emplace_back("17");
-    langStdMap["CUDA"].emplace_back("14");
-    langStdMap["CUDA"].emplace_back("11");
-    langStdMap["CUDA"].emplace_back("03");
-  }
-
-  std::string standard(*standardProp);
-  if (lang == "CUDA" && standard == "98") {
-    standard = "03";
-  }
-  std::vector<std::string>& stds = langStdMap[lang];
-
-  auto stdIt = std::find(stds.begin(), stds.end(), standard);
-  if (stdIt == stds.end()) {
-
-    std::string e =
-      lang + "_STANDARD is set to invalid value '" + standard + "'";
-    this->GetGlobalGenerator()->GetCMakeInstance()->IssueMessage(
-      MessageType::FATAL_ERROR, e, target->GetBacktrace());
-    return;
-  }
-
-  auto defaultStdIt = std::find(stds.begin(), stds.end(), defaultStd);
-  if (defaultStdIt == stds.end()) {
-    std::string e = "CMAKE_" + lang +
-      "_STANDARD_DEFAULT is set to invalid value '" + std::string(defaultStd) +
-      "'";
-    this->IssueMessage(MessageType::INTERNAL_ERROR, e);
-    return;
-  }
-
-  // If the standard requested is older than the compiler's default
-  // then we need to use a flag to change it.  The comparison is
-  // greater-or-equal because the standards are stored in backward
-  // chronological order.
-  if (stdIt >= defaultStdIt) {
-    std::string option_flag =
-      "CMAKE_" + lang + *stdIt + "_" + type + "_COMPILE_OPTION";
-
-    std::string const& opt =
-      target->Target->GetMakefile()->GetRequiredDefinition(option_flag);
-    std::vector<std::string> optVec = cmExpandedList(opt);
-    for (std::string const& i : optVec) {
-      this->AppendFlagEscape(flags, i);
-    }
-    return;
-  }
-
-  // The standard requested is at least as new as the compiler's default,
-  // and the standard request is not required.  Decay to the newest standard
-  // for which a flag is defined.
-  for (; stdIt < defaultStdIt; ++stdIt) {
-    std::string option_flag =
-      cmStrCat("CMAKE_", lang, *stdIt, "_", type, "_COMPILE_OPTION");
-
-    if (const char* opt =
-          target->Target->GetMakefile()->GetDefinition(option_flag)) {
-      std::vector<std::string> optVec = cmExpandedList(opt);
-      for (std::string const& i : optVec) {
-        this->AppendFlagEscape(flags, i);
-      }
-      return;
-    }
   }
 }
 

Source/cmStandardLevelResolver.cxx

@@ -7,6 +7,7 @@
 #include <cassert>
 #include <cstddef>
 #include <sstream>
+#include <stdexcept>
 #include <unordered_map>
 #include <utility>
 #include <vector>
@@ -45,10 +46,126 @@ struct StandardNeeded
 
 struct StanardLevelComputer
 {
-  explicit StanardLevelComputer(std::string lang, std::vector<int> levels)
+  explicit StanardLevelComputer(std::string lang, std::vector<int> levels,
+                                std::vector<std::string> levelsStr)
     : Language(std::move(lang))
     , Levels(std::move(levels))
+    , LevelsAsStrings(std::move(levelsStr))
   {
+    assert(levels.size() == levelsStr.size());
+  }
+
+  std::string GetCompileOptionDef(cmMakefile* makefile,
+                                  cmGeneratorTarget const* target,
+                                  std::string const& config) const
+  {
+
+    const auto& stds = this->Levels;
+    const auto& stdsStrings = this->LevelsAsStrings;
+
+    const char* defaultStd = makefile->GetDefinition(
+      cmStrCat("CMAKE_", this->Language, "_STANDARD_DEFAULT"));
+    if (!defaultStd || !*defaultStd) {
+      // this compiler has no notion of language standard levels
+      return std::string{};
+    }
+
+    bool ext = true;
+    if (cmProp extPropValue = target->GetLanguageExtensions(this->Language)) {
+      if (cmIsOff(*extPropValue)) {
+        ext = false;
+      }
+    }
+
+    cmProp standardProp = target->GetLanguageStandard(this->Language, config);
+    if (!standardProp) {
+      if (ext) {
+        // No language standard is specified and extensions are not disabled.
+        // Check if this compiler needs a flag to enable extensions.
+        return cmStrCat("CMAKE_", this->Language, "_EXTENSION_COMPILE_OPTION");
+      }
+      return std::string{};
+    }
+
+    std::string const type = ext ? "EXTENSION" : "STANDARD";
+
+    if (target->GetLanguageStandardRequired(this->Language)) {
+      std::string option_flag = cmStrCat(
+        "CMAKE_", this->Language, *standardProp, "_", type, "_COMPILE_OPTION");
+
+      const char* opt =
+        target->Target->GetMakefile()->GetDefinition(option_flag);
+      if (!opt) {
+        std::ostringstream e;
+        e << "Target \"" << target->GetName()
+          << "\" requires the language "
+             "dialect \""
+          << this->Language << *standardProp << "\" "
+          << (ext ? "(with compiler extensions)" : "")
+          << ", but CMake "
+             "does not know the compile flags to use to enable it.";
+        makefile->IssueMessage(MessageType::FATAL_ERROR, e.str());
+      }
+      return option_flag;
+    }
+
+    std::string standardStr(*standardProp);
+    if (this->Language == "CUDA" && standardStr == "98") {
+      standardStr = "03";
+    }
+
+    int standardValue = -1;
+    int defaultValue = -1;
+    try {
+      standardValue = std::stoi(standardStr);
+      defaultValue = std::stoi(defaultStd);
+    } catch (std::invalid_argument&) {
+      // fall through as we want an error
+      // when we can't find the bad value in the `stds` vector
+    }
+
+    auto stdIt = std::find(cm::cbegin(stds), cm::cend(stds), standardValue);
+    if (stdIt == cm::cend(stds)) {
+      std::string e =
+        cmStrCat(this->Language, "_STANDARD is set to invalid value '",
+                 standardStr, "'");
+      makefile->GetCMakeInstance()->IssueMessage(MessageType::FATAL_ERROR, e,
+                                                 target->GetBacktrace());
+      return std::string{};
+    }
+
+    auto defaultStdIt =
+      std::find(cm::cbegin(stds), cm::cend(stds), defaultValue);
+    if (defaultStdIt == cm::cend(stds)) {
+      std::string e = cmStrCat("CMAKE_", this->Language,
+                               "_STANDARD_DEFAULT is set to invalid value '",
+                               defaultStd, "'");
+      makefile->IssueMessage(MessageType::INTERNAL_ERROR, e);
+      return std::string{};
+    }
+
+    // If the standard requested is older than the compiler's default
+    // then we need to use a flag to change it.
+    if (stdIt <= defaultStdIt) {
+      auto offset = std::distance(cm::cbegin(stds), stdIt);
+      return cmStrCat("CMAKE_", this->Language, stdsStrings[offset], "_", type,
+                      "_COMPILE_OPTION");
+    }
+
+    // The standard requested is at least as new as the compiler's default,
+    // and the standard request is not required.  Decay to the newest standard
+    // for which a flag is defined.
+    for (; defaultStdIt < stdIt; --stdIt) {
+      auto offset = std::distance(cm::cbegin(stds), stdIt);
+      std::string option_flag =
+        cmStrCat("CMAKE_", this->Language, stdsStrings[offset], "_", type,
+                 "_COMPILE_OPTION");
+      if (target->Target->GetMakefile()->GetDefinition(option_flag)) {
+        return option_flag;
+      }
+    }
+
+    return std::string{};
   }
 
   bool GetNewRequiredStandard(cmMakefile* makefile,
@@ -99,7 +216,7 @@ struct StanardLevelComputer
       // the needed C++ features.
       if (existingLevelIter == cm::cend(this->Levels) ||
           existingLevelIter < this->Levels.begin() + needed.index) {
-        newRequiredStandard = std::to_string(this->Levels[needed.index]);
+        newRequiredStandard = this->LevelsAsStrings[needed.index];
       }
     }
 
@@ -163,8 +280,8 @@ struct StanardLevelComputer
     std::string prefix = cmStrCat("CMAKE_", this->Language);
     StandardNeeded maxLevel = { -1, -1 };
     for (size_t i = 0; i < this->Levels.size(); ++i) {
-      if (const char* prop = makefile->GetDefinition(cmStrCat(
-            prefix, std::to_string(this->Levels[i]), "_COMPILE_FEATURES"))) {
+      if (const char* prop = makefile->GetDefinition(
+            cmStrCat(prefix, this->LevelsAsStrings[i], "_COMPILE_FEATURES"))) {
         std::vector<std::string> props = cmExpandedList(prop);
         if (cm::contains(props, feature)) {
           maxLevel = { static_cast<int>(i), this->Levels[i] };
@@ -185,22 +302,44 @@ struct StanardLevelComputer
 
   std::string Language;
   std::vector<int> Levels;
+  std::vector<std::string> LevelsAsStrings;
 };
 
 std::unordered_map<std::string, StanardLevelComputer> StandardComputerMapping =
   {
-    { "C", StanardLevelComputer{ "C", std::vector<int>{ 90, 99, 11 } } },
+    { "C",
+      StanardLevelComputer{ "C", std::vector<int>{ 90, 99, 11 },
+                            std::vector<std::string>{ "90", "99", "11" } } },
     { "CXX",
-      StanardLevelComputer{ "CXX", std::vector<int>{ 98, 11, 14, 17, 20 } } },
+      StanardLevelComputer{
+        "CXX", std::vector<int>{ 98, 11, 14, 17, 20 },
+        std::vector<std::string>{ "98", "11", "14", "17", "20" } } },
     { "CUDA",
-      StanardLevelComputer{ "CUDA", std::vector<int>{ 03, 11, 14, 17, 20 } } },
-    { "OBJC", StanardLevelComputer{ "OBJC", std::vector<int>{ 90, 99, 11 } } },
+      StanardLevelComputer{
+        "CUDA", std::vector<int>{ 03, 11, 14, 17, 20 },
+        std::vector<std::string>{ "03", "11", "14", "17", "20" } } },
+    { "OBJC",
+      StanardLevelComputer{ "OBJC", std::vector<int>{ 90, 99, 11 },
+                            std::vector<std::string>{ "90", "99", "11" } } },
     { "OBJCXX",
-      StanardLevelComputer{ "OBJCXX",
-                            std::vector<int>{ 98, 11, 14, 17, 20 } } },
+      StanardLevelComputer{
+        "OBJCXX", std::vector<int>{ 98, 11, 14, 17, 20 },
+        std::vector<std::string>{ "98", "11", "14", "17", "20" } } },
   };
 }
 
+std::string cmStandardLevelResolver::GetCompileOptionDef(
+  cmGeneratorTarget const* target, std::string const& lang,
+  std::string const& config) const
+{
+  const auto& mapping = StandardComputerMapping.find(lang);
+  if (mapping == cm::cend(StandardComputerMapping)) {
+    return std::string{};
+  }
+
+  return mapping->second.GetCompileOptionDef(this->Makefile, target, config);
+}
+
 bool cmStandardLevelResolver::AddRequiredTargetFeature(
   cmTarget* target, const std::string& feature, std::string* error) const
 {

Source/cmStandardLevelResolver.h

@@ -20,6 +20,10 @@ public:
   {
   }
 
+  std::string GetCompileOptionDef(cmGeneratorTarget const* target,
+                                  std::string const& lang,
+                                  std::string const& config) const;
+
   bool AddRequiredTargetFeature(cmTarget* target, const std::string& feature,
                                 std::string* error = nullptr) const;
 

Tests/RunCMake/try_compile/CudaStandard-stderr.txt

@@ -1,5 +1,5 @@
 ^CMake Error at .*/Tests/RunCMake/try_compile/CudaStandard-build/CMakeFiles/CMakeTmp/CMakeLists.txt:[0-9]+ \(add_executable\):
-  CUDA_STANDARD is set to invalid value '3'
+  CUDA_STANDARD is set to invalid value '4'
 +
 CMake Error at CudaStandard.cmake:[0-9]+ \(try_compile\):
   Failed to generate test project build system.

Tests/RunCMake/try_compile/CudaStandard.cmake

@@ -1,7 +1,7 @@
 enable_language(CUDA)
 try_compile(result ${CMAKE_CURRENT_BINARY_DIR}
   SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/src.cu
-  CUDA_STANDARD 3
+  CUDA_STANDARD 4
   OUTPUT_VARIABLE out
   )
 message("try_compile output:\n${out}")