Experimental: Avoid mutating statically allocated data

Source/cmExperimental.cxx

@@ -7,6 +7,7 @@
 #include <cstddef>
 #include <string>
 
+#include "cmGlobalGenerator.h"
 #include "cmMakefile.h"
 #include "cmMessageType.h"
 #include "cmValue.h"
@@ -18,7 +19,7 @@ namespace {
  * Search for other instances to keep the documentation and test suite
  * up-to-date.
  */
-cmExperimental::FeatureData LookupTable[] = {
+cmExperimental::FeatureData const LookupTable[] = {
   // ExportPackageDependencies
   { "ExportPackageDependencies",
     "1942b4fa-b2c5-4546-9385-83f254070067",
@@ -26,8 +27,7 @@ cmExperimental::FeatureData LookupTable[] = {
     "CMake's EXPORT_PACKAGE_DEPENDENCIES support is experimental. It is meant "
     "only for experimentation and feedback to CMake developers.",
     {},
-    cmExperimental::TryCompileCondition::Always,
-    false },
+    cmExperimental::TryCompileCondition::Always },
   // WindowsKernelModeDriver
   { "WindowsKernelModeDriver",
     "9157bf90-2313-44d6-aefa-67cd83c8be7c",
@@ -35,8 +35,7 @@ cmExperimental::FeatureData LookupTable[] = {
     "CMake's Windows kernel-mode driver support is experimental. It is meant "
     "only for experimentation and feedback to CMake developers.",
     {},
-    cmExperimental::TryCompileCondition::Always,
-    false },
+    cmExperimental::TryCompileCondition::Always },
   // CxxImportStd
   { "CxxImportStd",
     "d0edc3af-4c50-42ea-a356-e2862fe7a444",
@@ -44,8 +43,7 @@ cmExperimental::FeatureData LookupTable[] = {
     "CMake's support for `import std;` in C++23 and newer is experimental. It "
     "is meant only for experimentation and feedback to CMake developers.",
     {},
-    cmExperimental::TryCompileCondition::Always,
-    false },
+    cmExperimental::TryCompileCondition::Always },
   // ImportPackageInfo
   { "ImportPackageInfo",
     "e82e467b-f997-4464-8ace-b00808fff261",
@@ -54,8 +52,7 @@ cmExperimental::FeatureData LookupTable[] = {
     "Specification format (via find_package) is experimental. It is meant "
     "only for experimentation and feedback to CMake developers.",
     {},
-    cmExperimental::TryCompileCondition::Always,
-    false },
+    cmExperimental::TryCompileCondition::Always },
   // ExportPackageInfo
   { "ExportPackageInfo",
     "b80be207-778e-46ba-8080-b23bba22639e",
@@ -64,8 +61,7 @@ cmExperimental::FeatureData LookupTable[] = {
     "Specification format is experimental. It is meant only for "
     "experimentation and feedback to CMake developers.",
     {},
-    cmExperimental::TryCompileCondition::Always,
-    false },
+    cmExperimental::TryCompileCondition::Always },
   // ExportBuildDatabase
   { "ExportBuildDatabase",
     "73194a1d-c0b5-41b9-9190-a4512925e192",
@@ -73,8 +69,7 @@ cmExperimental::FeatureData LookupTable[] = {
     "CMake's support for exporting build databases is experimental. It is "
     "meant only for experimentation and feedback to CMake developers.",
     {},
-    cmExperimental::TryCompileCondition::Never,
-    false },
+    cmExperimental::TryCompileCondition::Never },
   // Instrumentation
   { "Instrumentation",
     "a37d1069-1972-4901-b9c9-f194aaf2b6e0",
@@ -82,14 +77,13 @@ cmExperimental::FeatureData LookupTable[] = {
     "CMake's support for collecting instrumentation data is experimental. It "
     "is meant only for experimentation and feedback to CMake developers.",
     {},
-    cmExperimental::TryCompileCondition::Never,
-    false },
+    cmExperimental::TryCompileCondition::Never },
 };
 static_assert(sizeof(LookupTable) / sizeof(LookupTable[0]) ==
                 static_cast<size_t>(cmExperimental::Feature::Sentinel),
               "Experimental feature lookup table mismatch");
 
-cmExperimental::FeatureData& DataForFeature(cmExperimental::Feature f)
+cmExperimental::FeatureData const& DataForFeature(cmExperimental::Feature f)
 {
   assert(f != cmExperimental::Feature::Sentinel);
   return LookupTable[static_cast<size_t>(f)];
@@ -118,16 +112,16 @@ cm::optional<cmExperimental::Feature> cmExperimental::FeatureByName(
 bool cmExperimental::HasSupportEnabled(cmMakefile const& mf, Feature f)
 {
   bool enabled = false;
-  auto& data = ::DataForFeature(f);
+  FeatureData const& data = cmExperimental::DataForFeature(f);
 
-  auto value = mf.GetDefinition(data.Variable);
-  if (value == data.Uuid) {
-    enabled = true;
-  }
+  if (cmValue value = mf.GetDefinition(data.Variable)) {
+    enabled = *value == data.Uuid;
 
-  if (enabled && !data.Warned) {
-    mf.IssueMessage(MessageType::AUTHOR_WARNING, data.Description);
-    data.Warned = true;
+    if (mf.GetGlobalGenerator()->ShouldWarnExperimental(data.Name, *value)) {
+      if (enabled) {
+        mf.IssueMessage(MessageType::AUTHOR_WARNING, data.Description);
+      }
+    }
   }
 
   return enabled;

Source/cmExperimental.h

@@ -37,13 +37,12 @@ public:
 
   struct FeatureData
   {
-    std::string const Name;
-    std::string const Uuid;
-    std::string const Variable;
-    std::string const Description;
-    std::vector<std::string> const TryCompileVariables;
-    TryCompileCondition const ForwardThroughTryCompile;
-    bool Warned;
+    std::string Name;
+    std::string Uuid;
+    std::string Variable;
+    std::string Description;
+    std::vector<std::string> TryCompileVariables;
+    TryCompileCondition ForwardThroughTryCompile;
   };
 
   static FeatureData const& DataForFeature(Feature f);

Source/cmGlobalGenerator.cxx

@@ -2003,6 +2003,7 @@ void cmGlobalGenerator::ClearGeneratorMembers()
   this->GeneratedFiles.clear();
   this->RuntimeDependencySets.clear();
   this->RuntimeDependencySetsByName.clear();
+  this->WarnedExperimental.clear();
 }
 
 void cmGlobalGenerator::ComputeTargetObjectDirectory(
@@ -3914,3 +3915,11 @@ void cmGlobalGenerator::AddCMakeFilesToRebuild(
                this->InstallScripts.end());
   files.insert(files.end(), this->TestFiles.begin(), this->TestFiles.end());
 }
+
+bool cmGlobalGenerator::ShouldWarnExperimental(cm::string_view featureName,
+                                               cm::string_view featureUuid)
+{
+  return this->WarnedExperimental
+    .emplace(cmStrCat(featureName, '-', featureUuid))
+    .second;
+}

Source/cmGlobalGenerator.h

@@ -16,6 +16,7 @@
 #include <vector>
 
 #include <cm/optional>
+#include <cm/string_view>
 #include <cmext/algorithm>
 #include <cmext/string_view>
 
@@ -681,6 +682,9 @@ public:
     return configs;
   }
 
+  bool ShouldWarnExperimental(cm::string_view featureName,
+                              cm::string_view featureUuid);
+
 protected:
   // for a project collect all its targets by following depend
   // information, and also collect all the targets
@@ -908,6 +912,8 @@ private:
   // track targets to issue CMP0068 warning for.
   std::set<std::string> CMP0068WarnTargets;
 
+  std::unordered_set<std::string> WarnedExperimental;
+
   mutable std::map<cmSourceFile*, std::set<cmGeneratorTarget const*>>
     FilenameTargetDepends;