[Bug c++/116482] New: Bogus -Wunused-parameter with C++ coroutines

[Bug c++/116482] New: Bogus -Wunused-parameter with C++ coroutines

[daklishch at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116482

            Bug ID: 116482
           Summary: Bogus -Wunused-parameter with C++ coroutines
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: c++-coroutines
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: daklishch at gmail dot com
                CC: iains at gcc dot gnu.org
  Target Milestone: ---

After 6303cd7e41546e95c436bd274cc972674230fe1c, the following code produces
bogus -Wunused-parameter warning:

```
$ cat ../test.cpp 
#include <coroutine>

struct SuspendNever {
    bool await_ready();
    void await_suspend(std::coroutine_handle<>);
    void await_resume();
};

struct Coroutine;

struct PromiseType {
    Coroutine get_return_object();
    SuspendNever initial_suspend();
    SuspendNever final_suspend();
    void return_void();
};

struct Coroutine {
    using promise_type = PromiseType;
};

Coroutine __async_test_input_basic() {
    co_return;
}

$ ~/gcc-15-trunk/bin/g++ ../test.cpp -c -std=c++20 -fno-exceptions
-Wunused-parameter -o /dev/null
../test.cpp: In function ‘void
__async_test_input_basic(_Z24__async_test_input_basicv.Frame*)’:
../test.cpp:24:1: warning: unused parameter ‘frame_ptr’ [-Wunused-parameter]
   24 | }
      | ^
../test.cpp: In function ‘void
__async_test_input_basic(_Z24__async_test_input_basicv.Frame*)’:
../test.cpp:24:1: warning: unused parameter ‘frame_ptr’ [-Wunused-parameter]
```

CE link: https://godbolt.org/z/q85WMafja

[Bug c++/116482] Bogus -Wunused-parameter with C++ coroutines

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116482

Iain Sandoe <iains at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-08-26
             Status|UNCONFIRMED                 |NEW
   Target Milestone|---                         |15.0
     Ever confirmed|0                           |1

--- Comment #1 from Iain Sandoe <iains at gcc dot gnu.org> ---
confirmed

[Bug c++/116482] Bogus -Wunused-parameter with C++ coroutines

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116482

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Iain D Sandoe <iains@gcc.gnu.org>:

https://gcc.gnu.org/g:8d6d6c864442a1cc987b3e6bcb1d903ceb975e4a

commit r15-3211-g8d6d6c864442a1cc987b3e6bcb1d903ceb975e4a
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Mon Aug 26 14:09:40 2024 +0100

    c++, coroutines: The frame pointer is used in the helpers [PR116482].

    We have a bogus warning about the coroutine state frame pointers
    being apparently unused in the resume and destroy functions.  Fixed
    by making the parameters DECL_ARTIFICIAL.

            PR c++/116482

    gcc/cp/ChangeLog:

            * coroutines.cc
            (coro_build_actor_or_destroy_function): Make the parameter
            decls DECL_ARTIFICIAL.

    gcc/testsuite/ChangeLog:

            * g++.dg/coroutines/pr116482.C: New test.

    Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

[Bug c++/116482] Bogus -Wunused-parameter with C++ coroutines

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116482

Iain Sandoe <iains at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Iain Sandoe <iains at gcc dot gnu.org> ---
fixed