DeferredDiagnosticsEmitter crashes

[glevner]

Summary

Patch VisitCXXDeleteExpr() in clang::UsedDeclVisitor to avoid it crashing when the expression's destroyed type is null. According to the comments in CXXDeleteExpr::getDestroyedType(), this can happen when the type to delete is a dependent type.

[glevner]

See https://bugs.llvm.org/show_bug.cgi?id=47742

[yaxunl]

Can we have a lit test? Thanks.

[glevner]

I'm sorry, but I don't know how to reproduce the problem in isolation. We are JIT-compiling fairly complex C++ code, and the crash sometimes occurs when, for example, an included header file is not found...

[yaxunl]

LGTM. Thanks.

[glevner]

Great. I don't have commit access though. If I did, I would love to commit it to the release branch, which is what we use...

[yaxunl]

I can help you commit it to trunk. For cherrypick to release branch, we may need help of @hans

[hans]

In D88949#2319392, @yaxunl wrote:

I can help you commit it to trunk. For cherrypick to release branch, we may need help of @hans

It's most likely too late for 11.0.0, but I will put it on my list of 11.0.1 candidates.

[glevner]

Good enough for us... Thanks, @hans and @yaxunl!

clang/lib/Sema/UsedDeclVisitor.h

void VisitCXXNewExpr(CXXNewExpr *E) {
     if (E->getOperatorDelete())
       asImpl().visitUsedDecl(E->getBeginLoc(), E->getOperatorDelete());
     Inherited::VisitCXXNewExpr(E);
   }
 
   void VisitCXXDeleteExpr(CXXDeleteExpr *E) {
     if (E->getOperatorDelete())
       asImpl().visitUsedDecl(E->getBeginLoc(), E->getOperatorDelete());
-    QualType Destroyed = S.Context.getBaseElementType(E->getDestroyedType());
+    QualType DestroyedOrNull = E->getDestroyedType();
+    if (!DestroyedOrNull.isNull()) {
+      QualType Destroyed = S.Context.getBaseElementType(DestroyedOrNull);
       if (const RecordType *DestroyedRec = Destroyed->getAs<RecordType>()) {
         CXXRecordDecl *Record = cast<CXXRecordDecl>(DestroyedRec->getDecl());
         asImpl().visitUsedDecl(E->getBeginLoc(), S.LookupDestructor(Record));
       }
+    }
 
     Inherited::VisitCXXDeleteExpr(E);
   }
 
   void VisitCXXConstructExpr(CXXConstructExpr *E) {
     asImpl().visitUsedDecl(E->getBeginLoc(), E->getConstructor());
     Inherited::VisitCXXConstructExpr(E);
   }