[clang] [BoundsSafety] WIP: Make 'counted_by' work for pointer fields; late parsing for 'counted_by' on decl attr position (PR #87596)

[Bill Wendling via cfe-commits]

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@@ -0,0 +1,54 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+#define __counted_by(f)  __attribute__((counted_by(f)))
+
+struct size_unknown;
+
+struct at_pointer {
+  int count;
+  struct size_unknown *__counted_by(count) buf; // expected-error{{'counted_by' cannot be applied to an sized type}}
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bwendling wrote:

This should be fine, because `count` is declared before use—unless I'm getting type attributes confused with field attributes.. Also, there's a grammar-o in the message: `to _an_ sized type`.

https://github.com/llvm/llvm-project/pull/87596