Clangd crash in Namer::VisitCXXMemberCallExpr() in InlayHints.cpp

[HighCommander4]

I'm getting a crash in this function.

I don't have a reduced test case at the moment, but just eyeballing the function, it's unconditionally dereferencing E->getMethodDecl() and E->getImplicitObjectArgument(), and either of those could potentially be null.

This is a regression from https://reviews.llvm.org/D155421 which introduced this code.

cc @sam-mccall, @hokein

[hokein]

Thanks. I think your analysis is right:

• it is unlikely that the parameter E of VisitCXXMemberCallExpr will be null
• E->getMethodDecl() could probably return nullptr (for invalid code)

We should make a sanity check for the E->getMethodDecl() there, it would be great to have a reproduced testcase, but if it is too hard, I think it is fine.

[HighCommander4]

Reduced testcase:

class A {};

using Predicate = bool(A::*)();
void foo(A* a, Predicate p) {
  if ((a->*p)()) {
  }
}

Note that this is valid code.

[HighCommander4]

When the call is through a pointer to a member, CXXMemberCallExpr::getCallee() is (after unwrapping parens) a BinaryOperator (with the operator being ->*).

getMethodDecl() only returns non-null if the callee is a MemberExpr.

[HighCommander4]

Proposed fix: llvm/llvm-project#76492