[Bug c++/95477] New: [coroutines] coroutine result object not properly freed

[Bug c++/95477] New: [coroutines] coroutine result object not properly freed

[natattak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95477

            Bug ID: 95477
           Summary: [coroutines] coroutine result object not properly
                    freed
           Product: gcc
           Version: 10.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: natattak at gmail dot com
  Target Milestone: ---

In some cases, the result object of a coroutine is not properly destroyed after
the coroutine finishes execution. Consider the following example:


#include <coroutine>

struct simple {
  static inline int alive = 0;
  simple() { ++alive; }
  simple(simple&&) { ++alive; }
  ~simple() { --alive; }

  struct promise_type {
    simple get_return_object() { return simple{}; }
    void return_void() {}
    void unhandled_exception() {}
    auto initial_suspend() noexcept { return std::suspend_never{}; }
    auto final_suspend() noexcept { return std::suspend_never{}; }
  };
};

simple f() { co_return; }

int main() {
  {
    f();
  }
  return simple::alive;
}


The return value should be 0, indicating that all created objects were
destroyed. However, when executing, I get the result 1. After commenting out
the move constructor, the return value is 0 as expected. 

See also:
https://stackoverflow.com/questions/62125871/simple-coroutine-leaking-with-gcc-10

This is compiled using `-std=c++20 -fcoroutines`.
My `gcc -v` is:

Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --with-isl
--with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit
--enable-cet=auto --enable-checking=release --enable-clocale=gnu
--enable-default-pie --enable-default-ssp --enable-gnu-indirect-function
--enable-gnu-unique-object --enable-install-libiberty --enable-linker-build-id
--enable-lto --enable-multilib --enable-plugin --enable-shared
--enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-libunwind-exceptions --disable-werror
gdc_include_dir=/usr/include/dlang/gdc
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.1.0 (GCC)

[Bug c++/95477] [coroutines] coroutine result object not properly freed

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95477

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-06-03
             Status|UNCONFIRMED                 |NEW
   Target Milestone|---                         |10.2
           Keywords|                            |wrong-code
     Ever confirmed|0                           |1

--- Comment #1 from Iain Sandoe <iains at gcc dot gnu.org> ---
thanks for the report
it looks like I omitted a cleanup expression.

[Bug c++/95477] [coroutines] coroutine result object not properly freed

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95477

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lewissbaker.opensource@gmai
                   |                            |l.com

--- Comment #2 from Iain Sandoe <iains at gcc dot gnu.org> ---
*** Bug 95598 has been marked as a duplicate of this bug. ***

[Bug c++/95477] [coroutines] coroutine result object not properly freed

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95477

--- Comment #3 from CVS 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:788b962aa00959e861b45767c5c88ec41ca30c21

commit r11-1613-g788b962aa00959e861b45767c5c88ec41ca30c21
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Tue Jun 23 10:06:21 2020 +0100

    coroutines: Add a cleanup expression for g-r-o when needed [PR95477].

    The PR reports that we fail to destroy the object initially created from
    the get-return-object call.  Fixed by adding a cleanup when the DTOR is
    non-trivial.  In addition, to meet the specific wording that the call to
    get_return_object creates the glvalue for the return, we must construct
    that in-place in the return object to avoid a second copy/move CTOR.

    gcc/cp/ChangeLog:

            PR c++/95477
            * coroutines.cc (morph_fn_to_coro): Apply a cleanup to
            the get return object when the DTOR is non-trivial.

    gcc/testsuite/ChangeLog:

            PR c++/95477
            * g++.dg/coroutines/pr95477.C: New test.
            * g++.dg/coroutines/void-gro-non-class-coro.C: New test.

[Bug c++/95477] [coroutines] coroutine result object not properly freed

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95477

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Iain D Sandoe
<iains@gcc.gnu.org>:

https://gcc.gnu.org/g:d9b3aa517bdab280bbde2a80a80a77ad7333a0cb

commit r10-8369-gd9b3aa517bdab280bbde2a80a80a77ad7333a0cb
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Thu Jun 25 14:33:23 2020 +0100

    coroutines: Add a cleanup expression for g-r-o when needed [PR95477].

    The PR reports that we fail to destroy the object initially created from
    the get-return-object call.  Fixed by adding a cleanup when the DTOR is
    non-trivial.  In addition, to meet the specific wording that the call to
    get_return_object creates the glvalue for the return, we must construct
    that in-place in the return object to avoid a second copy/move CTOR.

    gcc/cp/ChangeLog:

            PR c++/95477
            * coroutines.cc (morph_fn_to_coro): Apply a cleanup to
            the get return object when the DTOR is non-trivial.

    gcc/testsuite/ChangeLog:

            PR c++/95477
            * g++.dg/coroutines/pr95477.C: New test.
            * g++.dg/coroutines/void-gro-non-class-coro.C: New test.

    (cherry picked from commit 788b962aa00959e861b45767c5c88ec41ca30c21)

[Bug c++/95477] [coroutines] coroutine result object not properly freed

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95477

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

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

--- Comment #5 from Iain Sandoe <iains at gcc dot gnu.org> ---
fixed for master and 10.2