[clang] Don't fail ExecuteCompilerInvocation() due to caller errors

[jansvoboda11]

This PR changes the behavior of clang::ExecuteCompilerInvocation() so that it only returns early when the DiagnosticsEngine emitted errors within the function. Handling errors emitted before the function got called is a responsibility of the caller. Necessary for #158381.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Jan Svoboda (jansvoboda11)

Changes

This PR changes the behavior of clang::ExecuteCompilerInvocation() so that it doesn't return early whenever the DiagnosticsEngine emitted errors before the function got called. Handling that situation is the responsibility of the caller. Necessary for #158381.

---

Full diff: https://github.com/llvm/llvm-project/pull/158695.diff

1 Files Affected:

• (modified) clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp (+3-1)

diff --git a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
index 9a6844d5f7d40..f1965a4e27e07 100644
--- a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
+++ b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
@@ -210,6 +210,8 @@ CreateFrontendAction(CompilerInstance &CI) {
 }
 
 bool ExecuteCompilerInvocation(CompilerInstance *Clang) {
+  unsigned NumErrorsBefore = Clang->getDiagnostics().getNumErrors();
+
   // Honor -help.
   if (Clang->getFrontendOpts().ShowHelp) {
     driver::getDriverOptTable().printHelp(
@@ -293,7 +295,7 @@ bool ExecuteCompilerInvocation(CompilerInstance *Clang) {
 #endif
 
   // If there were errors in processing arguments, don't do anything else.
-  if (Clang->getDiagnostics().hasErrorOccurred())
+  if (Clang->getDiagnostics().getNumErrors() != NumErrorsBefore)
     return false;
   // Create and execute the frontend action.
   std::unique_ptr<FrontendAction> Act(CreateFrontendAction(*Clang));

[cachemeifyoucan]

Can you add more comment to explain when do we actually call this function when Diagnostics Engine already has error? This will help to evaluate what is a right thing to do.

[jansvoboda11]

Currently we don't, but with #158381 we'll try to initialize the VFS overlays before calling clang::ExecuteCompilerInvocation(). If that VFS initialization fails, we still want to run the frontend action as per clang/test/VFS/module_missing_vfs.m and 005c2e5. Blindly checking hasErrorOccurred() without scope stops the compilation very soon instead of continuing. Note that right now, we initialize VFS overlays deep within this function under ExecuteAction(), so the hasErrorOccurred() logic doesn't affect it.

[cachemeifyoucan]

Can you summarize the reason and leave a comment in the code?