Sema: check for null TInfo in ActOnBaseSpecifier

[zarko]

Summary

In certain cases (particularly when some input files are missing), GetTypeFromParser will set TInfo to nullptr in ActOnBaseSpecifier.

[MaskRay]

This needs a reduced test case to demonstrate the problem and ensure clang will not regress in the future.

[rsmith]

I think the problem this aims to address was fixed by rG330873230071ffc2aebc0fe74db55e7a530c2f1b.

[zarko]

I can confirm that this has been fixed by the revision that rsmith has linked. Thanks!

clang/lib/Sema/SemaDeclCXX.cpp

for (const ParsedAttr &AL : Attributes) {
     Diag(AL.getLoc(), AL.getKind() == ParsedAttr::UnknownAttribute
                           ? (unsigned)diag::warn_unknown_attribute_ignored
                           : (unsigned)diag::err_base_specifier_attribute)
         << AL;
   }
 
   TypeSourceInfo *TInfo = nullptr;
   GetTypeFromParser(basetype, &TInfo);
+  if (TInfo == nullptr)
+    return true;
 
   if (EllipsisLoc.isInvalid() &&
       DiagnoseUnexpandedParameterPack(SpecifierRange.getBegin(), TInfo,
                                       UPPC_BaseType))
     return true;
 
   if (CXXBaseSpecifier *BaseSpec = CheckBaseSpecifier(Class, SpecifierRange,
                                                       Virtual, Access, TInfo,