Merge topic 'cxxmodules-no-unity'

63bbb3768d cmLocalGenerator: ignore scanned sources for unity builds
76b5383123 cmGlobalGenerator: add unity sources after computing target compile features
7fc2a83fe6 Tests/CXXModules: add a test with unity build support

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !9118

3 files changed, 39 insertions, 1 deletions

diff --git a/Source/cmGlobalGenerator.cxx b/Source/cmGlobalGenerator.cxx
index e74a8b0..8a07073 100644
--- a/Source/cmGlobalGenerator.cxx
+++ b/Source/cmGlobalGenerator.cxx
@@ -1612,6 +1612,13 @@ bool cmGlobalGenerator::Compute()
     }
   }
 
+  // Add unity sources after computing compile features.  Unity sources do
+  // not change the set of languages or features, but we need to know them
+  // to filter out sources that are scanned for C++ module dependencies.
+  if (!this->AddUnitySources()) {
+    return false;
+  }
+
   for (const auto& localGen : this->LocalGenerators) {
     cmMakefile* mf = localGen->GetMakefile();
     for (const auto& g : mf->GetInstallGenerators()) {
@@ -1888,7 +1895,6 @@ bool cmGlobalGenerator::AddAutomaticSources()
       if (!gt->CanCompileSources()) {
         continue;
       }
-      lg->AddUnityBuild(gt.get());
       lg->AddISPCDependencies(gt.get());
       // Targets that reuse a PCH are handled below.
       if (!gt->GetProperty("PRECOMPILE_HEADERS_REUSE_FROM")) {
@@ -1920,6 +1926,28 @@ bool cmGlobalGenerator::AddAutomaticSources()
   return true;
 }
 
+bool cmGlobalGenerator::AddUnitySources()
+{
+  for (const auto& lg : this->LocalGenerators) {
+    for (const auto& gt : lg->GetGeneratorTargets()) {
+      if (!gt->CanCompileSources()) {
+        continue;
+      }
+      lg->AddUnityBuild(gt.get());
+    }
+  }
+  // The above transformation may have changed the classification of sources.
+  // Clear the source list and classification cache (KindedSources) of all
+  // targets so that it will be recomputed correctly by the generators later
+  // now that the above transformations are done for all targets.
+  for (const auto& lg : this->LocalGenerators) {
+    for (const auto& gt : lg->GetGeneratorTargets()) {
+      gt->ClearSourcesCache();
+    }
+  }
+  return true;
+}
+
 std::unique_ptr<cmLinkLineComputer> cmGlobalGenerator::CreateLinkLineComputer(
   cmOutputConverter* outputConverter, cmStateDirectory const& stateDir) const
 {
diff --git a/Source/cmGlobalGenerator.h b/Source/cmGlobalGenerator.h
index d83b669..b1ce323 100644
--- a/Source/cmGlobalGenerator.h
+++ b/Source/cmGlobalGenerator.h
@@ -679,6 +679,7 @@ protected:
   bool AddHeaderSetVerification();
 
   bool AddAutomaticSources();
+  bool AddUnitySources();
 
   std::string SelectMakeProgram(const std::string& makeProgram,
                                 const std::string& makeDefault = "") const;
diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index 38c49ed..ab1de4f 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -3210,6 +3210,15 @@ void cmLocalGenerator::AddUnityBuild(cmGeneratorTarget* target)
     std::vector<cmSourceFile*> sources;
     target->GetSourceFiles(sources, configs[ci]);
     for (cmSourceFile* sf : sources) {
+      // Files which need C++ scanning cannot participate in unity builds as
+      // there is a single place in TUs that may perform module-dependency bits
+      // and a unity source cannot `#include` them in-order and represent a
+      // valid TU.
+      if (sf->GetLanguage() == "CXX"_s &&
+          target->NeedDyndepForSource("CXX", configs[ci], sf)) {
+        continue;
+      }
+
       auto mi = index.find(sf);
       if (mi == index.end()) {
         unitySources.emplace_back(sf);