[PATCH] coroutines: Copy attributes to the outlined functions [PR95518]

[Iain Sandoe]

Hi

We had omitted the copying of function attributes (including the
'used' status).  Mark the outlined functions as artificial, since
they are; some diagnostic processing tests this.

tested on Linux and Darwin,
OK for master?
10.2?
thanks
Iain

gcc/cp/ChangeLog:

        PR c++/95518
        * coroutines.cc (act_des_fn): Copy function attributes from
        the user’s function decl onto the outlined helpers.

gcc/testsuite/ChangeLog:

        PR c++/95518
        * g++.dg/coroutines/pr95518.C: New test.
---
 gcc/cp/coroutines.cc                      |  5 +++++
 gcc/testsuite/g++.dg/coroutines/pr95518.C | 27 +++++++++++++++++++++++
 2 files changed, 32 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/coroutines/pr95518.C

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index 93f1e5ca30d..4f7356e94e5 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -3530,12 +3530,17 @@ act_des_fn (tree orig, tree fn_type, tree 
coro_frame_ptr, const char* name)
   tree fn_name = get_fn_local_identifier (orig, name);
   tree fn = build_lang_decl (FUNCTION_DECL, fn_name, fn_type);
   DECL_CONTEXT (fn) = DECL_CONTEXT (orig);
+  DECL_ARTIFICIAL (fn) = true;
   DECL_INITIAL (fn) = error_mark_node;
   tree id = get_identifier ("frame_ptr");
   tree fp = build_lang_decl (PARM_DECL, id, coro_frame_ptr);
   DECL_CONTEXT (fp) = fn;
   DECL_ARG_TYPE (fp) = type_passed_as (coro_frame_ptr);
   DECL_ARGUMENTS (fn) = fp;
+  /* Copy used-ness from the original function.  */
+  TREE_USED (fn) = TREE_USED (orig);
+  /* Apply attributes from the original fn.  */
+  DECL_ATTRIBUTES (fn) = copy_list (DECL_ATTRIBUTES (orig));
   return fn;
 }
 
diff --git a/gcc/testsuite/g++.dg/coroutines/pr95518.C 
b/gcc/testsuite/g++.dg/coroutines/pr95518.C
new file mode 100644
index 00000000000..2d7dd049e1b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/coroutines/pr95518.C
@@ -0,0 +1,27 @@
+//  { dg-additional-options "-O -Wunused-function" }
+
+#if __has_include (<coroutine>)
+#include <coroutine>
+using namespace std;
+#elif defined (__clang__) && __has_include (<experimental/coroutine>)
+#include <experimental/coroutine>
+namespace std { using namespace experimental; }
+#endif
+
+struct dummy
+{
+    struct promise_type
+    {
+        dummy get_return_object() const noexcept { return {}; }
+        std::suspend_never initial_suspend() const noexcept { return {}; }
+        std::suspend_never final_suspend() const noexcept { return {}; }
+        void return_void() const noexcept {}
+        void unhandled_exception() const noexcept {}
+    };
+    int i; // work around #95516
+};
+
+[[maybe_unused]] static dummy foo()
+{ 
+    co_return;
+}
-- 
2.24.1