[llvm-branch-commits] [clang] [BoundsSafety] Support the counted_by family on function parameters (PR #234941)

[Dan Liew via llvm-branch-commits]

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@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -verify %s -ast-dump | FileCheck %s
+// RUN: %clang_cc1 -fexperimental-late-parse-attributes -verify %s -ast-dump | FileCheck %s
+
+#define __counted_by(f)  __attribute__((counted_by(f)))
+
+int global_count;
+
+// CHECK: FunctionDecl {{.*}} back_ref 'void (int, int * __counted_by(count))'
+// CHECK-NEXT: ParmVarDecl {{.*}} count 'int'
+// CHECK-NEXT: ParmVarDecl {{.*}} buf 'int * __counted_by(count)':'int *'
+void back_ref(int count, int *__counted_by(count) buf);
+
+// A rejected count is not applied, and the function stays valid.
+// CHECK: FunctionDecl {{.*}} not_a_param 'void (int *)'
+// expected-error at +1{{count expression in function declaration may only reference function parameters}}
+void not_a_param(int *__counted_by(global_count) buf);
+
+// A count on a K&R parameter declaration is dropped.
+// CHECK: FunctionDecl {{.*}} knr 'void (int, int *)'
+// expected-warning at +1{{a function definition without a prototype is deprecated}}
+void knr(count, buf) int count; int *__counted_by(count) buf; {}
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delcypher wrote:

I'm not sure if it's easy to do from the point where we drop the attribute but if possible we should emit a diagnostic here that attribute is ignored. There should be an existing diagnostic type for this already.

https://github.com/llvm/llvm-project/pull/234941