[Bug c++/94701] New: coroutines: Wrong code for structured bindings.

[Bug c++/94701] New: coroutines: Wrong code for structured bindings.

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94701

            Bug ID: 94701
           Summary: coroutines: Wrong code for structured bindings.
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: iains at gcc dot gnu.org
  Target Milestone: ---

Created attachment 48330
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48330&action=edit
patch under test

As reported by Michał Dominiak, the following code gets an incorrect answer -
this is because we fail to check for DECL_VALUE_EXPR in the handling for local
vars.

struct promise;

struct future
{
  using promise_type = promise;
};

struct promise
{
  template<typename... Args>
  promise (Args&... args) {}

  coro::suspend_never initial_suspend() { return {}; }
  coro::suspend_never final_suspend() { return {}; }

  future get_return_object() { return {}; }

  void return_value(int) {}
  void unhandled_exception() {}
};

#include <cassert>

struct pair
{
  int i;
};

pair 
something ()
{
  return { 1 };
}

future 
my_coro ()
{   
  auto ret = something ();
  assert(ret.i == 1);

  auto [ i ] = something ();
  assert(i == 1);

  co_return 1;
}

int main ()
{
  my_coro ();
}

[Bug c++/94701] coroutines: Wrong code for structured bindings.

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94701

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |iains at gcc dot gnu.org
   Last reconfirmed|                            |2020-04-21
   Target Milestone|---                         |10.0
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
           Keywords|                            |wrong-code

[Bug c++/94701] coroutines: Wrong code for structured bindings.

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94701

--- Comment #1 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:174b6f735019a11017284aaa23962cebd3943c99

commit r10-8002-g174b6f735019a11017284aaa23962cebd3943c99
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Mon Apr 27 23:55:00 2020 +0100

    coroutines: Fix for uses of structured binding [PR94701]

    Structured binding makes use of the DECL_VALUE_EXPR fields
    in local variables.  We need to recognise these and only amend
    the expression values, retaining the 'alias' value intact.

    gcc/cp/ChangeLog:

    2020-04-27  Iain Sandoe  <iain@sandoe.co.uk>

            PR c++/94701
            * coroutines.cc (struct local_var_info): Add fields for static
            variables and those with DECL_VALUE_EXPR redirection.
            (transform_local_var_uses):  Skip past typedefs and static vars
            and then account for redirected variables.
            (register_local_var_uses): Likewise.

    gcc/testsuite/ChangeLog:

    2020-04-27  Iain Sandoe  <iain@sandoe.co.uk>

            PR c++/94701
            * g++.dg/coroutines/torture/local-var-06-structured-binding.C: New
test.

[Bug c++/94701] coroutines: Wrong code for structured bindings.

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94701

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

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

--- Comment #2 from Iain Sandoe <iains at gcc dot gnu.org> ---
fixed on master.