[PATCH] D100667: [clang] Fix assert() crash when checking undeduced arg alignment

[Adam Czachorowski via Phabricator via cfe-commits]

adamcz added inline comments.


================
Comment at: clang/lib/Sema/SemaChecking.cpp:4543
   // getTypeAlignInChars requires complete types
-  if (ParamTy->isIncompleteType() || ArgTy->isIncompleteType() ||
-      ParamTy->isUndeducedType() || ArgTy->isUndeducedType())
+  auto CheckTypeOK = [](QualType Ty) {
+    if (Ty->isIncompleteType() || Ty->isUndeducedType())
----------------
hokein wrote:
> The current fix is on top of kadir's fix, now the code becomes more add-hoc, it looks like a smell to me.
> 
> 
> It looks like `CheckArgAlignment` has an implicit invariant (the arg type should never be undeduced), and this invariant was enforced by dropping the invalid AST. Now with `RecoveryExpr`, we might break the invariant -- when the RecoveryExpr preserves an `undeduced` type, like the test case in this patch (which is done via the [code](https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/SemaExprCXX.cpp#L1420)).
> 
> 
> I think a right fix is to fix in the `RecoveryExpr` side, `RecoveryExpr` should not preserve an undeduced type, we did it for function return type already (https://reviews.llvm.org/D87350), but it didn't cover all places. I think a general fixing place is `Sema::CreateRecoveryExpr`, if the passing `T` is undeduced, fallback to dependent type.
> 
Ooh, interesting. Thanks for the info.

I updated the change to catch this in CreateRecoveryExpr as well. I kept my original changes too, they shouldn't harm anything and it's better than crashing.

Let me know what you think about this now.


Repository:
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  https://reviews.llvm.org/D100667/new/

https://reviews.llvm.org/D100667