[Bug c++/101243] New: Coroutine lambda capture is destroyed twice

[Bug c++/101243] New: Coroutine lambda capture is destroyed twice

[victor.burckel at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101243

            Bug ID: 101243
           Summary: Coroutine lambda capture is destroyed twice
           Product: gcc
           Version: 11.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: victor.burckel at gmail dot com
  Target Milestone: ---

In a corourtine expecting a std::function<void()> parameter, passing a
temporary lambda with a capture results in the capture being destroyed twice:
See it on gldbolt, gcc vs clang outputs
https://godbolt.org/z/jx9Yh5cqM

#include <fmt/core.h>

#include <coroutine>
#include <functional>

#ifdef __clang__
namespace std::experimental {
using std::coroutine_handle;
using std::coroutine_traits;
}  // namespace std::experimental
#endif

struct task {
  struct promise_type;
  using handle_type = std::coroutine_handle<promise_type>;

  struct promise_type {
    auto initial_suspend() noexcept { return std::suspend_always{}; }
    auto final_suspend() noexcept { return std::suspend_always{}; }
    void return_void() noexcept {}
    task get_return_object() noexcept {
      return task{handle_type::from_promise(*this)};
    }
    void unhandled_exception() noexcept {}
  };

  task(handle_type h) : h{h} {}
  ~task() {
    if (h) {
      fmt::print("destroying coroutine\n");
      h.destroy();
      fmt::print("coroutine destroyed\n");
    }
  }

  bool await_ready() const noexcept { return false; }
  bool await_suspend(std::coroutine_handle<>) noexcept {
    h.resume();
    return true;
  }
  void await_resume() noexcept {}

  void resume() { h.resume(); }

  handle_type h;
};

struct S {
  S() { fmt::print("S::S()\n"); }
  S(const S&) { fmt::print("S::S(const S&)\n"); }
  S(S&&) { fmt::print("S::S(S&&)\n"); }
  ~S() { fmt::print("S::~S()\n"); }
};

task g(std::function<void()>) {
  fmt::print("in g()\n");
  co_return;
}

task f() {
  fmt::print("calling g()\n");
  co_await g([s=S{}] {});
  fmt::print("g called\n");
}

int main() {
  auto task = f();
  fmt::print("resuming f\n");
  task.resume();
  fmt::print("resuming f\n");
  task.resume();
}

Gcc outputs:
resuming f
calling g()
S::S()
S::S(S&&)
in g()
resuming f
destroying coroutine
S::~S()
coroutine destroyed
S::~S()
S::~S()
g called
destroying coroutine
coroutine destroyed

While clang outputs:
resuming f
calling g()
S::S()
S::S(S&&)
in g()
resuming f
destroying coroutine
S::~S()
coroutine destroyed
S::~S()
g called
destroying coroutine
coroutine destroyed

[Bug c++/101243] Coroutine lambda capture is destroyed twice

[victor.burckel at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101243

--- Comment #1 from Victor Burckel <victor.burckel at gmail dot com> ---
May be similar to 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99576
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98401

[Bug c++/101243] Coroutine lambda capture is destroyed twice

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101243

--- Comment #2 from Iain Sandoe <iains at gcc dot gnu.org> ---
(In reply to Victor Burckel from comment #1)
> May be similar to 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99576
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98401

I agree this is likely to be a duplicate ( I am in the process of reviewing
coros bugs)

[Bug c++/101243] Coroutine lambda capture is destroyed twice

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101243

Nathan Sidwell <nathan at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |nathan at gcc dot gnu.org

--- Comment #3 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
Created attachment 51358
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51358&action=edit
move-only type

Modified to make the capture a move-only type

devvm1702:323>./cc1plus -std=c++20 pr.ii -quiet              
pr.cc: In function 'task f()':
pr.cc:73:1: warning: 'f()::_Z1fv.Frame' has a field
'f()::_Z1fv.Frame::D.48642_2_3' whose type has no linkage [-Wsubobject-linkage]
In file included from
/data/users/nathans/tools/include/c++/10.1.1/functional:59,
                 from pr.cc:2:
/data/users/nathans/tools/include/c++/10.1.1/bits/std_function.h: In
instantiation of 'static void
std::_Function_base::_Base_manager<_Functor>::_M_clone(std::_Any_data&, const
std::_Any_data&, std::false_type) [with _Functor =
f(f()::_Z1fv.Frame*)::<lambda()>; std::false_type =
std::integral_constant<bool, false>]':
/data/users/nathans/tools/include/c++/10.1.1/bits/std_function.h:196:16:  
required from 'static bool
std::_Function_base::_Base_manager<_Functor>::_M_manager(std::_Any_data&, const
std::_Any_data&, std::_Manager_operation) [with _Functor =
f(f()::_Z1fv.Frame*)::<lambda()>]'
/data/users/nathans/tools/include/c++/10.1.1/bits/std_function.h:283:23:  
required from 'static bool std::_Function_handler<_Res(_ArgTypes ...),
_Functor>::_M_manager(std::_Any_data&, const std::_Any_data&,
std::_Manager_operation) [with _Res = void; _Functor =
f(f()::_Z1fv.Frame*)::<lambda()>; _ArgTypes = {}]'
/data/users/nathans/tools/include/c++/10.1.1/bits/std_function.h:611:19:  
required from 'std::function<_Res(_ArgTypes ...)>::function(_Functor) [with
_Functor = f(f()::_Z1fv.Frame*)::<lambda()>; <template-parameter-2-2> = void;
<template-parameter-2-3> = void; _Res = void; _ArgTypes = {}]'
pr.cc:71:13:   required from here
/data/users/nathans/tools/include/c++/10.1.1/bits/std_function.h:161:13: error:
use of deleted function 'f(f()::_Z1fv.Frame*)::<lambda()>::<lambda>(const
f(f()::_Z1fv.Frame*)::<lambda()>&)'
  161 |             new _Functor(*__source._M_access<const _Functor*>());
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pr.cc:71:22: note: 'f(f()::_Z1fv.Frame*)::<lambda()>::<lambda>(const
f(f()::_Z1fv.Frame*)::<lambda()>&)' is implicitly deleted because the default
definition would be ill-formed:
pr.cc:71:22: error: use of deleted function 'FOO::FOO(const FOO&)'
pr.cc:59:3: note: declared here

[Bug c++/101243] Coroutine lambda capture is destroyed twice

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101243

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Nathan Sidwell from comment #3)
> pr.cc:71:22: error: use of deleted function 'FOO::FOO(const FOO&)'
> pr.cc:59:3: note: declared here

Maybe I'm missing the point of the code, but this is expected, isn't it?
std::function cannot store move-only callables, it requires them to be
copyable.

[Bug c++/101243] Coroutine lambda capture is destroyed twice

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101243

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
For the attachment in comment 3 trunk now says:

In file included from /home/jwakely/gcc/12/include/c++/12.0.0/functional:59,
                 from /tmp/pr-1.cc:2:
/home/jwakely/gcc/12/include/c++/12.0.0/bits/std_function.h: In instantiation
of 'std::function<_Res(_ArgTypes ...)>::function(_Functor&&) [with _Functor =
f(f()::_Z1fv.frame*)::<lambda()>; <template-parameter-2-2> = void; _Res = void;
_ArgTypes = {}]':
/tmp/pr-1.cc:71:13:   required from here
/home/jwakely/gcc/12/include/c++/12.0.0/bits/std_function.h:442:69: error:
static assertion failed: std::function target must be copy-constructible
  442 |          
static_assert(is_copy_constructible<__decay_t<_Functor>>::value,
      |                                                                    
^~~~~
/home/jwakely/gcc/12/include/c++/12.0.0/bits/std_function.h:442:69: note:
'std::integral_constant<bool, false>::value' evaluates to false

[Bug c++/101243] Coroutine lambda capture is destroyed twice

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101243

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #6 from Iain Sandoe <iains at gcc dot gnu.org> ---
this appears to be the same issue as 100611

*** This bug has been marked as a duplicate of bug 100611 ***