================
@@ -132,9 +132,20 @@ bool Sema::CheckCountedByAttrOnField(FieldDecl *FD, Expr
*E, bool CountInBytes,
// `BoundsSafetyCheckUseOfCountAttrPtr`
//
// * When the pointee type is always an incomplete type (e.g.
- // `void`) the attribute is disallowed by this method because we know the
- // type can never be completed so there's no reason to allow it.
- InvalidTypeKind = CountedByInvalidPointeeTypeKind::INCOMPLETE;
+ // `void` in strict C mode) the attribute is disallowed by this method
+ // because we know the type can never be completed so there's no reason
+ // to allow it.
+ //
+ // Exception: In GNU mode, void has an implicit size of 1 byte for pointer
+ // arithmetic. Therefore, counted_by on void* is allowed as a GNU extension
+ // and behaves equivalently to sized_by (treating the count as bytes).
+ bool IsVoidPtrInGNUMode = PointeeTy->isVoidType() && getLangOpts().GNUMode;
+ if (IsVoidPtrInGNUMode) {
+ // Emit a warning that this is a GNU extension
+ Diag(FD->getBeginLoc(), diag::ext_gnu_counted_by_void_ptr) << Kind;
----------------
delcypher wrote:
On this path we should probably add
```
assert(InvalidTypeKind == CountedByInvalidPointeeTypeKind::VALID);
```
or explicitly make that assignment for clarity.
https://github.com/llvm/llvm-project/pull/164737
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