[PATCH] D146426: [Sema] Fix crash on __fp16 parameters in template instantiations

Tue Mar 21 02:31:21 PDT 2023

ilya-biryukov added a comment.

In D146426#4207423 <https://reviews.llvm.org/D146426#4207423>, @shafik wrote:

> As I noted in the bug report not doing `D.setInvalidType();` does fix this bug and seems harmless since the error diagnostic should prevent us from getting to codegen but it is not clear to me if this has other negative impacts. Reading your replies it is not obvious you looked at this path or not.

There are too many other code paths that set `setInvalidType()`, I'll try to add more tests that capture those too.
It would be easy to avoid calling `setInvalidType()` for `__fp16` in particular, but checking for nulls actually saves us from other potential crashes .

> I would not mind a quick fix but I think we should have a plan for a more correct fix before we do that.

Based on conversations in this thread, I think the right way is to make sure parameter lists never have nulls.
One way to fix this is to make sure we always fill parameters with non-null values, even if `GetTypeSourceInfoForDeclarator` does not get called.
An alternative way would be to call `GetTypeSourceInfoForDeclarator` even for invalid types (IIUC, it can perfectly handle function types, but other types also fail there).

I'll try to explore some these fixes and try to come up with a follow-up change.

Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D146426/new/

https://reviews.llvm.org/D146426