[Bug c++/95895] New: internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[Bug c++/95895] New: internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[gleb at scylladb dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

            Bug ID: 95895
           Summary: internal compiler error: in captures_temporary, at
                    cp/coroutines.cc:2717
           Product: gcc
           Version: 10.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gleb at scylladb dot com
  Target Milestone: ---

Got an internal compile error:
raft/raft.cc: In member function ‘seastar::future<>
raft::server::drop_leadership(raft::server::state)’:
raft/raft.cc:173:1: internal compiler error: in captures_temporary, at
cp/coroutines.cc:2717
  173 | }
      | ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://bugzilla.redhat.com/bugzilla> for instructions.
Preprocessed source stored into /tmp/ccdd6MK7.out file, please attach this to
your bugreport.
ninja: build stopped: subcommand failed.

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[gleb at scylladb dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

--- Comment #1 from Gleb Natapov <gleb at scylladb dot com> ---
Created attachment 48783
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48783&action=edit
File that gcc asked to attach

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-06-25
     Ever confirmed|0                           |1
                 CC|                            |iains at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
Confirmed, I'm bisecting that..

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Reduced test-case:

cat x.ii
namespace std {
template <typename> struct remove_reference;
template <typename _Tp> struct remove_reference<_Tp &> { typedef _Tp type; };
template <typename _Tp> remove_reference<_Tp>::type move(_Tp &&);
template <typename _Tp> class optional {
public:
  _Tp *operator->();
};
class vector {
public:
  int begin();
  int end();
};
} // namespace std
template <typename...> class future { future(future &&); };
namespace internal {
struct extract_values_from_futures_vector {
  using future_type = future<>;
  static future_type current_exception_as_future();
};
} // namespace internal
template <typename FutureIterator>
auto when_all_succeed(FutureIterator, FutureIterator) {
  using result_transform = internal::extract_values_from_futures_vector;
  return result_transform::current_exception_as_future();
}
namespace std {
template <typename...> struct coroutine_traits;
template <typename = void> struct coroutine_handle;
template <> struct coroutine_handle<> {};
template <typename> struct coroutine_handle : coroutine_handle<> {};
struct suspend_never {
  void await_ready();
  void await_suspend(coroutine_handle<>);
  void await_resume();
};
} // namespace std
namespace internal {
class coroutine_traits_base {
public:
  class promise_type {
  public:
    std::suspend_never initial_suspend();
    std::suspend_never final_suspend();
  };
};
struct awaiter {
  future<> _future;
  void await_ready();
  template <typename U> void await_suspend(std::coroutine_handle<U>);
  void await_resume();
};
} // namespace internal
auto operator co_await(future<> f) { return internal::awaiter(std::move(f)); }
namespace std {
template <typename... T, typename... Args>
class coroutine_traits<future<T...>, Args...>
    : public internal::coroutine_traits_base {};
class server {
  struct leader_state {
    vector _replicatoin_fibers;
  };
  optional<leader_state> _leader_state;
  future<> drop_leadership();
};
future<> server::drop_leadership() {
  co_await when_all_succeed(_leader_state->_replicatoin_fibers.begin(),
                            _leader_state->_replicatoin_fibers.end());

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

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
           Keywords|                            |ice-on-valid-code
   Target Milestone|---                         |10.2

--- Comment #4 from Iain Sandoe <iains at gcc dot gnu.org> ---
thanks for the report.

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

--- Comment #5 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:0f66b8486cea8668020e4bd48f261b760cb579be

commit r11-2183-g0f66b8486cea8668020e4bd48f261b760cb579be
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Sat Jul 11 08:49:33 2020 +0100

    coroutines: Correct frame capture of compiler temps [PR95591+4].

    When a full expression contains a co_await (or co_yield), this means
    that it might be suspended; which would destroy temporary variables
    (on a stack for example).  However the language guarantees that such
    temporaries are live until the end of the expression.

    In order to preserve this, we 'promote' temporaries where necessary
    so that they are saved in the coroutine frame (which allows them to
    remain live potentially until the frame is destroyed).  In addition,
    sub-expressions that produce control flow (such as TRUTH_AND/OR_IF
    or COND_EXPR) must be handled specifically to ensure that await
    expressions are properly expanded.

    This patch corrects two mistakes in which we were (a) failing to
    promote some temporaries and (b) we we failing to sequence DTORs for
    the captures properly. This manifests in a number of related (but not
    exact duplicate) PRs.

    The revised code collects the actions into one place and maps all the
    control flow into one form - a benefit of this is that co_returns are
    now expanded earlier (which provides an opportunity to address PR95517
    in some future patch).

    We replace a statement that contains await expression(s) with a bind
    scope that has a variable list describing the temporaries that have
    been 'promoted' and a statement list that contains a series of cleanup
    expressions for each of those.  Where we encounter nested conditional
    expressions, these are wrapped in a try-finally block with a guard var
    for each sub-expression variable that needs a DTOR.  The guards are all
    declared and initialized to false before the first conditional sub-
    expression.  The 'finally' block contains a series of if blocks (one
    per guard variable) enclosing the relevant DTOR.

    Variables listed in a bind scope in this manner are automatically moved
    to a coroutine frame version by existing code (so we re-use that rather
    than having a separate mechanism).

    gcc/cp/ChangeLog:

            PR c++/95591
            PR c++/95599
            PR c++/95823
            PR c++/95824
            PR c++/95895
            * coroutines.cc (struct coro_ret_data): Delete.
            (coro_maybe_expand_co_return): Delete.
            (co_return_expander): Delete.
            (expand_co_returns): Delete.
            (co_await_find_in_subtree): Remove unused name.
            (build_actor_fn): Remove unused parm, remove handling
            for co_return expansion.
            (register_await_info): Demote duplicate info message to a
            warning.
            (coro_make_frame_entry): Move closer to use site.
            (struct susp_frame_data): Add fields for final suspend label
            and a flag to indicate await expressions with initializers.
            (captures_temporary): Delete.
            (register_awaits): Remove unused code, update comments.
            (find_any_await): New.
            (tmp_target_expr_p): New.
            (struct interesting): New.
            (find_interesting_subtree): New.
            (struct var_nest_node): New.
            (flatten_await_stmt): New.
            (handle_nested_conditionals): New.
            (process_conditional): New.
            (replace_statement_captures): Rename to...
            (maybe_promote_temps): ... this.
            (maybe_promote_captured_temps): Delete.
            (analyze_expression_awaits): Check for await expressions with
            initializers.  Simplify handling for truth-and/or-if.
            (expand_one_truth_if): Simplify (map cases that need expansion
            to COND_EXPR).
            (await_statement_walker): Handle CO_RETURN_EXPR. Simplify the
            handling for truth-and/or-if expressions.
            (register_local_var_uses): Ensure that we create names in the
            implementation namespace.
            (morph_fn_to_coro): Add final suspend label to suspend frame
            callback data and remove it from the build_actor_fn call.

    gcc/testsuite/ChangeLog:

            PR c++/95591
            PR c++/95599
            PR c++/95823
            PR c++/95824
            PR c++/95895
            * g++.dg/coroutines/pr95591.C: New test.
            * g++.dg/coroutines/pr95599.C: New test.
            * g++.dg/coroutines/pr95823.C: New test.
            * g++.dg/coroutines/pr95824.C: New test.

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[avi@cloudius-systems.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

Avi Kivity <avi@cloudius-systems.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |avi@cloudius-systems.com

--- Comment #6 from Avi Kivity <avi@cloudius-systems.com> ---
Requesting a backport to gcc 10.

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

--- Comment #7 from Iain Sandoe <iains at gcc dot gnu.org> ---
(In reply to Avi Kivity from comment #6)
> Requesting a backport to gcc 10.

the 10.x branch is closed right now for 10.2 release.

the back port will be done after 10.2 has released and the branch is re-opened
 (of course you can cherry-pick it onto 10.2 as well)

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.2                        |10.3

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10.2 is released, adjusting target milestone.

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

--- Comment #9 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:f43a1b1d1718969423337190ddbbbc9037c67783

commit r10-8545-gf43a1b1d1718969423337190ddbbbc9037c67783
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Sun Jul 19 18:39:21 2020 +0100

    coroutines: Correct frame capture of compiler temps [PR95591+4].

    When a full expression contains a co_await (or co_yield), this means
    that it might be suspended; which would destroy temporary variables
    (on a stack for example).  However the language guarantees that such
    temporaries are live until the end of the expression.

    In order to preserve this, we 'promote' temporaries where necessary
    so that they are saved in the coroutine frame (which allows them to
    remain live potentially until the frame is destroyed).  In addition,
    sub-expressions that produce control flow (such as TRUTH_AND/OR_IF
    or COND_EXPR) must be handled specifically to ensure that await
    expressions are properly expanded.

    This patch corrects two mistakes in which we were (a) failing to
    promote some temporaries and (b) we we failing to sequence DTORs for
    the captures properly. This manifests in a number of related (but not
    exact duplicate) PRs.

    The revised code collects the actions into one place and maps all the
    control flow into one form - a benefit of this is that co_returns are
    now expanded earlier (which provides an opportunity to address PR95517
    in some future patch).

    We replace a statement that contains await expression(s) with a bind
    scope that has a variable list describing the temporaries that have
    been 'promoted' and a statement list that contains a series of cleanup
    expressions for each of those.  Where we encounter nested conditional
    expressions, these are wrapped in a try-finally block with a guard var
    for each sub-expression variable that needs a DTOR.  The guards are all
    declared and initialized to false before the first conditional sub-
    expression.  The 'finally' block contains a series of if blocks (one
    per guard variable) enclosing the relevant DTOR.

    Variables listed in a bind scope in this manner are automatically moved
    to a coroutine frame version by existing code (so we re-use that rather
    than having a separate mechanism).

    gcc/cp/ChangeLog:

            PR c++/95591
            PR c++/95599
            PR c++/95823
            PR c++/95824
            PR c++/95895
            * coroutines.cc (struct coro_ret_data): Delete.
            (coro_maybe_expand_co_return): Delete.
            (co_return_expander): Delete.
            (expand_co_returns): Delete.
            (co_await_find_in_subtree): Remove unused name.
            (build_actor_fn): Remove unused parm, remove handling
            for co_return expansion.
            (register_await_info): Demote duplicate info message to a
            warning.
            (coro_make_frame_entry): Move closer to use site.
            (struct susp_frame_data): Add fields for final suspend label
            and a flag to indicate await expressions with initializers.
            (captures_temporary): Delete.
            (register_awaits): Remove unused code, update comments.
            (find_any_await): New.
            (tmp_target_expr_p): New.
            (struct interesting): New.
            (find_interesting_subtree): New.
            (struct var_nest_node): New.
            (flatten_await_stmt): New.
            (handle_nested_conditionals): New.
            (process_conditional): New.
            (replace_statement_captures): Rename to...
            (maybe_promote_temps): ... this.
            (maybe_promote_captured_temps): Delete.
            (analyze_expression_awaits): Check for await expressions with
            initializers.  Simplify handling for truth-and/or-if.
            (expand_one_truth_if): Simplify (map cases that need expansion
            to COND_EXPR).
            (await_statement_walker): Handle CO_RETURN_EXPR. Simplify the
            handling for truth-and/or-if expressions.
            (register_local_var_uses): Ensure that we create names in the
            implementation namespace.
            (morph_fn_to_coro): Add final suspend label to suspend frame
            callback data and remove it from the build_actor_fn call.

    gcc/testsuite/ChangeLog:

            PR c++/95591
            PR c++/95599
            PR c++/95823
            PR c++/95824
            PR c++/95895
            * g++.dg/coroutines/pr95591.C: New test.
            * g++.dg/coroutines/pr95599.C: New test.
            * g++.dg/coroutines/pr95823.C: New test.
            * g++.dg/coroutines/pr95824.C: New test.

    (cherry picked from commit 0f66b8486cea8668020e4bd48f261b760cb579be)

[Bug c++/95895] internal compiler error: in captures_temporary, at cp/coroutines.cc:2717

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95895

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

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

--- Comment #10 from Iain Sandoe <iains at gcc dot gnu.org> ---
fixed on master and for the 10.x branch.