[Lldb-commits] [lldb] [lldb] Fix expressions that involve nested structs/classes/unions. (PR #77029)

[Michael Buch via lldb-commits]

Michael137 wrote:

> But if it'd require substantial reengineering to clang to get this working - this seems an unfortunate regression to carry in the interim, and it might be worth reverting to the previous (differently buggy, but at least work-around-able) behavior.

To clarify, the regression @dwblaikie reported in https://github.com/llvm/llvm-project/issues/79668 was introduced in https://github.com/llvm/llvm-project/pull/74786, not in this current PR. IIUC, this PR just *partially* fixed https://github.com/llvm/llvm-project/issues/53904?

> The new flow could be:
> 
> * any struct/class gets created as a forward declaration and has the external AST source enabled
> * the external AST calls to complete the type when needed by expression parser or LLDB APIs
> * we complete the type
> * we leave the external AST enabled so we can get called for contained types
> 
> The last item here would require modifications to clang which could be debugger specific changes that are only enabled in a special debug compiler mode so they don't affect the actual compiler. Thoughts?

Following overview of the clang<->lldb call-chain might be useful: https://github.com/llvm/llvm-project/issues/53904#issuecomment-1877114034. Not sure I fully understand the "we leave the external AST enabled so we can get called for contained types" idea. Happy to chat about how to make this work though

https://github.com/llvm/llvm-project/pull/77029