[clang][modules] Validate input file format for GenerateModuleInterfaceAction (#132692)

clang/include/clang/Basic/DiagnosticFrontendKinds.td

@@ -260,6 +260,10 @@ def err_modules_embed_file_not_found :
   DefaultFatal;
 def err_module_header_file_not_found :
   Error<"module header file '%0' not found">, DefaultFatal;
+def err_frontend_action_unsupported_input_format
+    : Error<"%0 does not support input file format of file '%1': "
+            "'%select{Source|ModuleMap|Precompiled|Unknown}2'">,
+      DefaultFatal;
 
 def err_test_module_file_extension_version : Error<
   "test module file extension '%0' has different version (%1.%2) than expected "

clang/include/clang/Frontend/FrontendActions.h

@@ -156,6 +156,7 @@ class GenerateModuleFromModuleMapAction : public GenerateModuleAction {
 /// files) for C++20 Named Modules.
 class GenerateModuleInterfaceAction : public GenerateModuleAction {
 protected:
+  bool PrepareToExecuteAction(CompilerInstance &CI) override;
   bool BeginSourceFileAction(CompilerInstance &CI) override;
 
   std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,

clang/lib/Frontend/FrontendActions.cpp

@@ -263,6 +263,20 @@ GenerateModuleFromModuleMapAction::CreateOutputFile(CompilerInstance &CI,
                                     /*ForceUseTemporary=*/true);
 }
 
+bool GenerateModuleInterfaceAction::PrepareToExecuteAction(
+    CompilerInstance &CI) {
+  for (const auto &FIF : CI.getFrontendOpts().Inputs) {
+    if (const auto InputFormat = FIF.getKind().getFormat();
+        InputFormat != InputKind::Format::Source) {
+      CI.getDiagnostics().Report(
+          diag::err_frontend_action_unsupported_input_format)
+          << "module interface compilation" << FIF.getFile() << InputFormat;
+      return false;
+    }
+  }
+  return GenerateModuleAction::PrepareToExecuteAction(CI);
+}
+
 bool GenerateModuleInterfaceAction::BeginSourceFileAction(
     CompilerInstance &CI) {
   CI.getLangOpts().setCompilingModule(LangOptions::CMK_ModuleInterface);

clang/test/Modules/emit-module-interface-pcm-input.cpp

@@ -0,0 +1,13 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: cd %t
+
+// Related to issue #132692
+// Verify that clang_cc1 doesn't crash when trying to generate a module
+// interface from an alreay precompiled module (`.pcm`).
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface a.cppm -o a.pcm
+// RUN: not %clang_cc1 -std=c++20 -emit-module-interface a.pcm
+// RUN: not %clang_cc1 -std=c++20 -emit-reduced-module-interface a.pcm
+
+//--- a.cppm
+export module A;