Merge topic 'cxx-module-metadata'

fa10dc6c22 Experimental/CXXModules: Implement EcoStd Module Metadata parser

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !11422

Source/CMakeLists.txt

@@ -165,6 +165,8 @@ add_library(
   cmCustomCommandTypes.h
   cmCxxModuleMapper.cxx
   cmCxxModuleMapper.h
+  cmCxxModuleMetadata.cxx
+  cmCxxModuleMetadata.h
   cmCxxModuleUsageEffects.cxx
   cmCxxModuleUsageEffects.h
   cmDefinitions.cxx

Source/cmCxxModuleMetadata.cxx

@@ -0,0 +1,460 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file LICENSE.rst or https://cmake.org/licensing for details.  */
+
+#include "cmCxxModuleMetadata.h"
+
+#include <algorithm>
+#include <set>
+#include <string>
+#include <utility>
+
+#include <cmext/string_view>
+
+#include <cm3p/json/value.h>
+#include <cm3p/json/writer.h>
+
+#include "cmsys/FStream.hxx"
+
+#include "cmFileSet.h"
+#include "cmJSONState.h"
+#include "cmListFileCache.h"
+#include "cmStringAlgorithms.h"
+#include "cmSystemTools.h"
+#include "cmTarget.h"
+
+namespace {
+
+bool JsonIsStringArray(Json::Value const& v)
+{
+  return v.isArray() &&
+    std::all_of(v.begin(), v.end(),
+                [](Json::Value const& it) { return it.isString(); });
+}
+
+bool ParsePreprocessorDefine(Json::Value& dval,
+                             cmCxxModuleMetadata::PreprocessorDefineData& out,
+                             cmJSONState* state)
+{
+  if (!dval.isObject()) {
+    state->AddErrorAtValue("each entry in 'definitions' must be an object",
+                           &dval);
+    return false;
+  }
+
+  if (!dval.isMember("name") || !dval["name"].isString() ||
+      dval["name"].asString().empty()) {
+    state->AddErrorAtValue(
+      "preprocessor definition requires a non-empty 'name'", &dval["name"]);
+    return false;
+  }
+  out.Name = dval["name"].asString();
+
+  if (dval.isMember("value")) {
+    if (dval["value"].isString()) {
+      out.Value = dval["value"].asString();
+    } else if (!dval["value"].isNull()) {
+      state->AddErrorAtValue(
+        "'value' in preprocessor definition must be string or null",
+        &dval["value"]);
+      return false;
+    }
+  }
+
+  if (dval.isMember("undef")) {
+    if (!dval["undef"].isBool()) {
+      state->AddErrorAtValue(
+        "'undef' in preprocessor definition must be boolean", &dval["undef"]);
+      return false;
+    }
+    out.Undef = dval["undef"].asBool();
+  }
+
+  if (dval.isMember("vendor")) {
+    out.Vendor = std::move(dval["vendor"]);
+  }
+
+  return true;
+}
+
+bool ParseLocalArguments(Json::Value& lav,
+                         cmCxxModuleMetadata::LocalArgumentsData& out,
+                         cmJSONState* state)
+{
+  if (!lav.isObject()) {
+    state->AddErrorAtValue("'local-arguments' must be an object", &lav);
+    return false;
+  }
+
+  if (lav.isMember("include-directories")) {
+    if (!JsonIsStringArray(lav["include-directories"])) {
+      state->AddErrorAtValue(
+        "'include-directories' must be an array of strings",
+        &lav["include-directories"]);
+      return false;
+    }
+    for (auto const& s : lav["include-directories"]) {
+      out.IncludeDirectories.push_back(s.asString());
+    }
+  }
+
+  if (lav.isMember("system-include-directories")) {
+    if (!JsonIsStringArray(lav["system-include-directories"])) {
+      state->AddErrorAtValue(
+        "'system-include-directories' must be an array of strings",
+        &lav["system-include-directories"]);
+      return false;
+    }
+    for (auto const& s : lav["system-include-directories"]) {
+      out.SystemIncludeDirectories.push_back(s.asString());
+    }
+  }
+
+  if (lav.isMember("definitions")) {
+    if (!lav["definitions"].isArray()) {
+      state->AddErrorAtValue("'definitions' must be an array",
+                             &lav["definitions"]);
+      return false;
+    }
+    for (Json::Value& dval : lav["definitions"]) {
+      out.Definitions.emplace_back();
+      if (!ParsePreprocessorDefine(dval, out.Definitions.back(), state)) {
+        return false;
+      }
+    }
+  }
+
+  if (lav.isMember("vendor")) {
+    out.Vendor = std::move(lav["vendor"]);
+  }
+
+  return true;
+}
+
+bool ParseModule(Json::Value& mval, cmCxxModuleMetadata::ModuleData& mod,
+                 cmJSONState* state)
+{
+  if (!mval.isObject()) {
+    state->AddErrorAtValue("each entry in 'modules' must be an object", &mval);
+    return false;
+  }
+
+  if (!mval.isMember("logical-name") || !mval["logical-name"].isString() ||
+      mval["logical-name"].asString().empty()) {
+    state->AddErrorAtValue(
+      "module entries require a non-empty 'logical-name' string",
+      &mval["logical-name"]);
+    return false;
+  }
+  mod.LogicalName = mval["logical-name"].asString();
+
+  if (!mval.isMember("source-path") || !mval["source-path"].isString() ||
+      mval["source-path"].asString().empty()) {
+    state->AddErrorAtValue(
+      "module entries require a non-empty 'source-path' string",
+      &mval["source-path"]);
+    return false;
+  }
+  mod.SourcePath = mval["source-path"].asString();
+
+  if (mval.isMember("is-interface")) {
+    if (!mval["is-interface"].isBool()) {
+      state->AddErrorAtValue("'is-interface' must be boolean",
+                             &mval["is-interface"]);
+      return false;
+    }
+    mod.IsInterface = mval["is-interface"].asBool();
+  } else {
+    mod.IsInterface = true;
+  }
+
+  if (mval.isMember("is-std-library")) {
+    if (!mval["is-std-library"].isBool()) {
+      state->AddErrorAtValue("'is-std-library' must be boolean",
+                             &mval["is-std-library"]);
+      return false;
+    }
+    mod.IsStdLibrary = mval["is-std-library"].asBool();
+  } else {
+    mod.IsStdLibrary = false;
+  }
+
+  if (mval.isMember("local-arguments")) {
+    mod.LocalArguments.emplace();
+    if (!ParseLocalArguments(mval["local-arguments"], *mod.LocalArguments,
+                             state)) {
+      return false;
+    }
+  }
+
+  if (mval.isMember("vendor")) {
+    mod.Vendor = std::move(mval["vendor"]);
+  }
+
+  return true;
+}
+
+bool ParseRoot(Json::Value& root, cmCxxModuleMetadata& meta,
+               cmJSONState* state)
+{
+  if (!root.isMember("version") || !root["version"].isInt()) {
+    state->AddErrorAtValue(
+      "Top-level member 'version' is required and must be an integer", &root);
+    return false;
+  }
+  meta.Version = root["version"].asInt();
+
+  if (root.isMember("revision")) {
+    if (!root["revision"].isInt()) {
+      state->AddErrorAtValue("'revision' must be an integer",
+                             &root["revision"]);
+      return false;
+    }
+    meta.Revision = root["revision"].asInt();
+  }
+
+  if (root.isMember("modules")) {
+    if (!root["modules"].isArray()) {
+      state->AddErrorAtValue("'modules' must be an array", &root["modules"]);
+      return false;
+    }
+    for (Json::Value& mval : root["modules"]) {
+      meta.Modules.emplace_back();
+      if (!ParseModule(mval, meta.Modules.back(), state)) {
+        return false;
+      }
+    }
+  }
+
+  for (std::string& key : root.getMemberNames()) {
+    if (key == "version" || key == "revision" || key == "modules") {
+      continue;
+    }
+    meta.Extensions.emplace(std::move(key), std::move(root[key]));
+  }
+
+  return true;
+}
+
+} // namespace
+
+cmCxxModuleMetadata::ParseResult cmCxxModuleMetadata::LoadFromFile(
+  std::string const& path)
+{
+  ParseResult res;
+
+  Json::Value root;
+  cmJSONState parseState(path, &root);
+  if (!parseState.errors.empty()) {
+    res.Error = parseState.GetErrorMessage();
+    return res;
+  }
+
+  cmCxxModuleMetadata meta;
+  if (!ParseRoot(root, meta, &parseState)) {
+    res.Error = parseState.GetErrorMessage();
+    return res;
+  }
+
+  meta.MetadataFilePath = path;
+  res.Meta = std::move(meta);
+  return res;
+}
+
+namespace {
+
+Json::Value SerializePreprocessorDefine(
+  cmCxxModuleMetadata::PreprocessorDefineData const& d)
+{
+  Json::Value dv(Json::objectValue);
+  dv["name"] = d.Name;
+  if (d.Value) {
+    dv["value"] = *d.Value;
+  } else {
+    dv["value"] = Json::Value::null;
+  }
+  dv["undef"] = d.Undef;
+  if (d.Vendor) {
+    dv["vendor"] = *d.Vendor;
+  }
+  return dv;
+}
+
+Json::Value SerializeLocalArguments(
+  cmCxxModuleMetadata::LocalArgumentsData const& la)
+{
+  Json::Value lav(Json::objectValue);
+
+  if (!la.IncludeDirectories.empty()) {
+    Json::Value& inc = lav["include-directories"] = Json::arrayValue;
+    for (auto const& s : la.IncludeDirectories) {
+      inc.append(s);
+    }
+  }
+
+  if (!la.SystemIncludeDirectories.empty()) {
+    Json::Value& sinc = lav["system-include-directories"] = Json::arrayValue;
+    for (auto const& s : la.SystemIncludeDirectories) {
+      sinc.append(s);
+    }
+  }
+
+  if (!la.Definitions.empty()) {
+    Json::Value& defs = lav["definitions"] = Json::arrayValue;
+    for (auto const& d : la.Definitions) {
+      defs.append(SerializePreprocessorDefine(d));
+    }
+  }
+
+  if (la.Vendor) {
+    lav["vendor"] = *la.Vendor;
+  }
+
+  return lav;
+}
+
+Json::Value SerializeModule(cmCxxModuleMetadata::ModuleData const& m)
+{
+  Json::Value mv(Json::objectValue);
+  mv["logical-name"] = m.LogicalName;
+  mv["source-path"] = m.SourcePath;
+  mv["is-interface"] = m.IsInterface;
+  mv["is-std-library"] = m.IsStdLibrary;
+
+  if (m.LocalArguments) {
+    mv["local-arguments"] = SerializeLocalArguments(*m.LocalArguments);
+  }
+
+  if (m.Vendor) {
+    mv["vendor"] = *m.Vendor;
+  }
+
+  return mv;
+}
+
+} // namespace
+
+Json::Value cmCxxModuleMetadata::ToJsonValue(cmCxxModuleMetadata const& meta)
+{
+  Json::Value root(Json::objectValue);
+
+  root["version"] = meta.Version;
+  root["revision"] = meta.Revision;
+
+  Json::Value& modules = root["modules"] = Json::arrayValue;
+  for (auto const& m : meta.Modules) {
+    modules.append(SerializeModule(m));
+  }
+
+  for (auto const& kv : meta.Extensions) {
+    root[kv.first] = kv.second;
+  }
+
+  return root;
+}
+
+cmCxxModuleMetadata::SaveResult cmCxxModuleMetadata::SaveToFile(
+  std::string const& path, cmCxxModuleMetadata const& meta)
+{
+  SaveResult st;
+
+  cmsys::ofstream ofs(path.c_str());
+  if (!ofs.is_open()) {
+    st.Error = cmStrCat("Unable to open file for writing: "_s, path);
+    return st;
+  }
+
+  Json::StreamWriterBuilder wbuilder;
+  wbuilder["indentation"] = "  ";
+  ofs << Json::writeString(wbuilder, ToJsonValue(meta));
+
+  if (!ofs.good()) {
+    st.Error = cmStrCat("Write failed for file: "_s, path);
+    return st;
+  }
+
+  st.Ok = true;
+  return st;
+}
+
+void cmCxxModuleMetadata::PopulateTarget(
+  cmTarget& target, cmCxxModuleMetadata const& meta,
+  std::vector<std::string> const& configs)
+{
+  std::vector<cm::string_view> allIncludeDirectories;
+  std::vector<std::string> allCompileDefinitions;
+  std::set<std::string> baseDirs;
+
+  std::string metadataDir =
+    cmSystemTools::GetFilenamePath(meta.MetadataFilePath);
+
+  auto fileSet = target.GetOrCreateFileSet("CXX_MODULES", "CXX_MODULES",
+                                           cmFileSetVisibility::Interface);
+
+  for (auto const& module : meta.Modules) {
+    std::string sourcePath = module.SourcePath;
+    if (!cmSystemTools::FileIsFullPath(sourcePath)) {
+      sourcePath = cmStrCat(metadataDir, '/', sourcePath);
+    }
+
+    // Module metadata files can reference files in different roots,
+    // just use the immediate parent directory as a base directory
+    baseDirs.insert(cmSystemTools::GetFilenamePath(sourcePath));
+
+    fileSet.first->AddFileEntry(sourcePath);
+
+    if (module.LocalArguments) {
+      for (auto const& incDir : module.LocalArguments->IncludeDirectories) {
+        allIncludeDirectories.push_back(incDir);
+      }
+      for (auto const& sysIncDir :
+           module.LocalArguments->SystemIncludeDirectories) {
+        allIncludeDirectories.push_back(sysIncDir);
+      }
+
+      for (auto const& def : module.LocalArguments->Definitions) {
+        if (!def.Undef) {
+          if (def.Value) {
+            allCompileDefinitions.push_back(
+              cmStrCat(def.Name, "="_s, *def.Value));
+          } else {
+            allCompileDefinitions.push_back(def.Name);
+          }
+        }
+      }
+    }
+  }
+
+  for (auto const& baseDir : baseDirs) {
+    fileSet.first->AddDirectoryEntry(baseDir);
+  }
+
+  if (!allIncludeDirectories.empty()) {
+    target.SetProperty("IMPORTED_CXX_MODULES_INCLUDE_DIRECTORIES",
+                       cmJoin(allIncludeDirectories, ";"));
+  }
+
+  if (!allCompileDefinitions.empty()) {
+    target.SetProperty("IMPORTED_CXX_MODULES_COMPILE_DEFINITIONS",
+                       cmJoin(allCompileDefinitions, ";"));
+  }
+
+  for (auto const& config : configs) {
+    std::vector<std::string> moduleList;
+    for (auto const& module : meta.Modules) {
+      if (module.IsInterface) {
+        std::string sourcePath = module.SourcePath;
+        if (!cmSystemTools::FileIsFullPath(sourcePath)) {
+          sourcePath = cmStrCat(metadataDir, '/', sourcePath);
+        }
+        moduleList.push_back(cmStrCat(module.LogicalName, "="_s, sourcePath));
+      }
+    }
+
+    if (!moduleList.empty()) {
+      std::string upperConfig = cmSystemTools::UpperCase(config);
+      std::string propertyName =
+        cmStrCat("IMPORTED_CXX_MODULES_"_s, upperConfig);
+      target.SetProperty(propertyName, cmJoin(moduleList, ";"));
+    }
+  }
+}

Source/cmCxxModuleMetadata.h

@@ -0,0 +1,84 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file LICENSE.rst or https://cmake.org/licensing for details.  */
+#pragma once
+
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include <cm/optional>
+#include <cm/string_view>
+
+#include <cm3p/json/value.h>
+
+class cmTarget;
+
+class cmCxxModuleMetadata
+{
+public:
+  struct PreprocessorDefineData
+  {
+    std::string Name;
+    cm::optional<std::string> Value;
+    bool Undef = false;
+    cm::optional<Json::Value> Vendor;
+  };
+
+  struct LocalArgumentsData
+  {
+    std::vector<std::string> IncludeDirectories;
+    std::vector<std::string> SystemIncludeDirectories;
+    std::vector<PreprocessorDefineData> Definitions;
+    cm::optional<Json::Value> Vendor;
+  };
+
+  struct ModuleData
+  {
+    std::string LogicalName;
+    std::string SourcePath;
+    bool IsInterface = true;
+    bool IsStdLibrary = false;
+    cm::optional<LocalArgumentsData> LocalArguments;
+    cm::optional<Json::Value> Vendor;
+  };
+
+  int Version = 0;
+  int Revision = 0;
+  std::vector<ModuleData> Modules;
+  std::string MetadataFilePath;
+
+  std::unordered_map<std::string, Json::Value> Extensions;
+
+  struct ParseResult;
+
+  struct SaveResult
+  {
+    bool Ok = false;
+    std::string Error;
+    explicit operator bool() const { return Ok; }
+  };
+
+  static ParseResult LoadFromFile(std::string const& path);
+  static Json::Value ToJsonValue(cmCxxModuleMetadata const& meta);
+  static SaveResult SaveToFile(std::string const& path,
+                               cmCxxModuleMetadata const& meta);
+  static void PopulateTarget(cmTarget& target, cmCxxModuleMetadata const& meta,
+                             std::vector<std::string> const& configs);
+  static void PopulateTarget(cmTarget& target, cmCxxModuleMetadata const& meta,
+                             cm::string_view config)
+  {
+    PopulateTarget(target, meta,
+                   std::vector<std::string>{ std::string(config) });
+  }
+  static void PopulateTarget(cmTarget& target, cmCxxModuleMetadata const& meta)
+  {
+    PopulateTarget(target, meta, "NOCONFIG");
+  }
+};
+
+struct cmCxxModuleMetadata::ParseResult
+{
+  cm::optional<cmCxxModuleMetadata> Meta;
+  std::string Error;
+  explicit operator bool() const { return static_cast<bool>(Meta); }
+};

Source/cmGeneratorTarget.cxx

@@ -22,6 +22,7 @@
 #include "cmAlgorithms.h"
 #include "cmComputeLinkInformation.h" // IWYU pragma: keep
 #include "cmCryptoHash.h"
+#include "cmCxxModuleMetadata.h"
 #include "cmCxxModuleUsageEffects.h"
 #include "cmExperimental.h"
 #include "cmFileSet.h"
@@ -5126,6 +5127,70 @@ bool cmGeneratorTarget::IsNullImpliedByLinkLibraries(
   return cm::contains(this->LinkImplicitNullProperties, p);
 }
 
+namespace {
+bool CreateCxxStdlibTarget(cmMakefile* makefile, cmLocalGenerator* lg,
+                           std::string const& targetName,
+                           std::string const& cxxTargetName,
+                           std::string const& stdLevel,
+                           std::vector<std::string> const& configs)
+{
+#ifndef CMAKE_BOOTSTRAP
+
+  static cm::optional<cmCxxModuleMetadata> metadata;
+
+  // Load metadata only when we need to create a target
+  if (!metadata) {
+    auto errorMessage =
+      makefile->GetDefinition("CMAKE_CXX_COMPILER_IMPORT_STD_ERROR_MESSAGE");
+    if (!errorMessage.IsEmpty()) {
+      makefile->IssueMessage(
+        MessageType::FATAL_ERROR,
+        cmStrCat(R"(The "CXX_MODULE_STD" property on target ")", targetName,
+                 "\" requires toolchain support, but it was not provided.  "
+                 "Reason:\n  ",
+                 *errorMessage));
+      return false;
+    }
+
+    auto metadataPath =
+      makefile->GetDefinition("CMAKE_CXX_STDLIB_MODULES_JSON");
+    if (metadataPath.IsEmpty()) {
+      makefile->IssueMessage(
+        MessageType::FATAL_ERROR,
+        cmStrCat(
+          R"("The "CXX_MODULE_STD" property on target ")", targetName,
+          "\" requires CMAKE_CXX_STDLIB_MODULES_JSON be set, but it was not "
+          "provided by the toolchain."));
+      return false;
+    }
+
+    auto parseResult = cmCxxModuleMetadata::LoadFromFile(*metadataPath);
+    if (!parseResult) {
+      makefile->IssueMessage(
+        MessageType::FATAL_ERROR,
+        cmStrCat("Failed to load C++ standard library modules metadata "
+                 "from \"",
+                 *metadataPath, "\": ", parseResult.Error));
+      return false;
+    }
+
+    metadata = std::move(*parseResult.Meta);
+  }
+
+  auto* stdlibTgt = makefile->AddImportedTarget(
+    cxxTargetName, cmStateEnums::INTERFACE_LIBRARY, true);
+  cmCxxModuleMetadata::PopulateTarget(*stdlibTgt, *metadata, configs);
+  stdlibTgt->AppendProperty("IMPORTED_CXX_MODULES_COMPILE_FEATURES",
+                            cmStrCat("cxx_std_", stdLevel));
+
+  lg->AddGeneratorTarget(cm::make_unique<cmGeneratorTarget>(stdlibTgt, lg));
+
+#endif // CMAKE_BOOTSTRAP
+
+  return true;
+}
+} // namespace
+
 bool cmGeneratorTarget::ApplyCXXStdTargets()
 {
   cmStandardLevelResolver standardResolver(this->Makefile);
@@ -5207,35 +5272,33 @@ bool cmGeneratorTarget::ApplyCXXStdTargets()
 
     auto const stdLevel =
       standardResolver.GetLevelString("CXX", *explicitLevel);
-    auto const targetName = cmStrCat("__CMAKE::CXX", stdLevel);
-    if (!this->Makefile->FindTargetToUse(targetName)) {
-      auto basicReason = this->Makefile->GetDefinition(cmStrCat(
-        "CMAKE_CXX", stdLevel, "_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE"));
-      std::string reason;
-      if (!basicReason.IsEmpty()) {
-        reason = cmStrCat("  Reason:\n  ", basicReason);
-      }
-      this->Makefile->IssueMessage(
-        MessageType::FATAL_ERROR,
-        cmStrCat(R"(The "CXX_MODULE_STD" property on the target ")",
-                 this->GetName(), "\" requires that the \"", targetName,
-                 "\" target exist, but it was not provided by the toolchain.",
-                 reason));
-      break;
-    }
+    auto const cxxTargetName = cmStrCat("__CMAKE::CXX", stdLevel);
 
-    // Check the experimental feature here as well. A toolchain may have
-    // provided the target and skipped the check in the toolchain preparation
-    // logic.
-    if (!cmExperimental::HasSupportEnabled(
-          *this->Makefile, cmExperimental::Feature::CxxImportStd)) {
-      break;
+    // Create the __CMAKE::CXX## IMPORTED interface target if it doesn't
+    // already exist
+    if (!this->Makefile->FindTargetToUse(cxxTargetName) &&
+        !CreateCxxStdlibTarget(this->Makefile, this->LocalGenerator,
+                               this->GetName(), cxxTargetName, stdLevel,
+                               configs)) {
+      return false;
     }
 
     this->Target->AppendProperty(
       "LINK_LIBRARIES",
-      cmStrCat("$<BUILD_LOCAL_INTERFACE:$<$<CONFIG:", config, ">:", targetName,
-               ">>"));
+      cmStrCat("$<BUILD_LOCAL_INTERFACE:$<$<CONFIG:", config,
+               ">:", cxxTargetName, ">>"));
+  }
+
+  // Check the experimental feature here. A toolchain may have
+  // skipped the check in the toolchain preparation logic.
+  if (!cmExperimental::HasSupportEnabled(
+        *this->Makefile, cmExperimental::Feature::CxxImportStd)) {
+    this->Makefile->IssueMessage(
+      MessageType::FATAL_ERROR,
+      "Experimental `import std` support not enabled when detecting "
+      "toolchain; it must be set before `CXX` is enabled (usually a "
+      "`project()` call).");
+    return false;
   }
 
   return true;
@@ -5335,7 +5398,9 @@ bool cmGeneratorTarget::DiscoverSyntheticTargets(cmSyntheticTargetCache& cache,
         }
         // See `cmGlobalGenerator::ApplyCXXStdTargets` in
         // `cmGlobalGenerator::Compute` for non-synthetic target resolutions.
-        gtp->ApplyCXXStdTargets();
+        if (!gtp->ApplyCXXStdTargets()) {
+          return false;
+        }
 
         gtp->DiscoverSyntheticTargets(cache, config);
 

Source/cmGlobalGenerator.cxx

@@ -1787,7 +1787,17 @@ void cmGlobalGenerator::ComputeTargetOrder(cmGeneratorTarget const* gt,
 bool cmGlobalGenerator::ApplyCXXStdTargets()
 {
   for (auto const& gen : this->LocalGenerators) {
-    for (auto const& tgt : gen->GetGeneratorTargets()) {
+
+    // tgt->ApplyCXXStd can create targets itself, so we need iterators which
+    // won't be invalidated by that target creation
+    auto const& genTgts = gen->GetGeneratorTargets();
+    std::vector<cmGeneratorTarget*> existingTgts;
+    existingTgts.reserve(genTgts.size());
+    for (auto const& tgt : genTgts) {
+      existingTgts.push_back(tgt.get());
+    }
+
+    for (auto const& tgt : existingTgts) {
       if (!tgt->ApplyCXXStdTargets()) {
         return false;
       }