================
@@ -222,3 +222,49 @@ struct on_void_ty {
// expected-error@+1{{field has incomplete type 'void'}}
void wrong_ty __counted_by_or_null(count);
};
+
+//==============================================================================
+// __counted_by_or_null on pointer members in unions
+//==============================================================================
+
+// Pointer in anonymous union with count in parent struct - OK
+struct ptr_in_anon_union_count_in_parent {
+ int count;
+ union {
+ int a;
+ struct size_known *buf __counted_by_or_null(count);
+ };
+};
+
+// Pointer in named union - ERROR
+union ptr_in_named_union {
+ int count;
+ struct size_known *buf __counted_by_or_null(count); // expected-error
{{'counted_by_or_null' cannot be applied to a union member}}
+};
+
+// Both pointer and count in same anonymous union - ERROR (they share storage)
+struct ptr_and_count_in_same_anon_union {
+ union {
+ int count;
+ struct size_known *buf __counted_by_or_null(count); // expected-error
{{'counted_by_or_null' cannot be applied to a union member}}
+ };
+};
+
+// Count in anonymous union, pointer in parent struct - ERROR (count in union)
+struct count_in_anon_union_ptr_in_parent {
+ union {
+ int count;
+ int x;
+ };
+ struct size_known *buf __counted_by_or_null(count); // expected-error
{{'counted_by_or_null' argument cannot refer to a union member}}
+};
+
+// Count in anonymous union, but hidden by struct - ERROR (count in union)
+struct count_in_deep_anon_union {
+ union {
+ struct {
+ int count;
+ };
+ };
+ struct size_known *buf __counted_by_or_null(count); // expected-error
{{'counted_by_or_null' argument cannot refer to a union member}}
+};
----------------
ojhunt wrote:
The problem I have isn't specifically the intersecting storage, it's that it
becomes possible to mutate the count without doing so observably - this applies
to structs inside a union but I think we generally assume (for usability not an
actual expectation that no one does this) that people are interacting with the
struct type only.
e.g
```cpp
struct foo {
union {
int count;
int somethingElse;
};
struct bar *buf __counted_by(count);
};
void funk() {
foo f;
f.count1 = 10;
f.buf1 = calloc(10, sizeof(struct bar))
f.somethingElse = 15; // We don't see that this has made an incorrect change
to the reported size of buf
}
```
https://github.com/llvm/llvm-project/pull/171996
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