[Bug c++/101040] New: [11 Regression] Internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3571

[Bug c++/101040] New: [11 Regression] Internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3571

[git at foonathan dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101040

            Bug ID: 101040
           Summary: [11 Regression] Internal compiler error: in
                    get_or_insert_ctor_field, at cp/constexpr.c:3571
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: git at foonathan dot net
  Target Milestone: ---

Minimal repro: https://godbolt.org/z/n71dhjPox

```
// This class has to be empty.
struct empty
{};

// This class has to be empty.
struct single
{
    // This member has to be no_unique_address.
    [[no_unique_address]] empty obj;
};

// This class has to be empty and derived from single.
struct derived : single
{
    // This constructor has to be constexpr and take a forwarding reference.
    template <typename Arg>
    constexpr derived(Arg&& arg) : single{arg}
    {}
};

auto obj = derived{empty{}};
```

Fails on GCC 11.1 and trunk:

```
source>:21:27:   in 'constexpr' expansion of 'derived(empty())'
<source>:21:27: internal compiler error: in get_or_insert_ctor_field, at
cp/constexpr.c:3571
   21 | auto obj = derived{empty{}};
      |                           ^
0x1d322a9 internal_error(char const*, ...)
        ???:0
0x71fc09 fancy_abort(char const*, int, char const*)
        ???:0
0xa58de0 store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ???:0
0x818a14 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int)
        ???:0
0x94812d c_parse_file()
        ???:0
0xacb002 c_common_parse_file()
        ???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1
```

Works with GCC 10.3.

[Bug c++/101040] [11 Regression] Internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3571

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code
   Target Milestone|---                         |11.2
      Known to work|                            |10.3.0

[Bug c++/101040] [11/12 Regression] Internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3571 since r11-7980-gc3d3bb0f03dbd025

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
                 CC|                            |jason at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org
   Last reconfirmed|                            |2021-06-14
            Summary|[11 Regression] Internal    |[11/12 Regression] Internal
                   |compiler error: in          |compiler error: in
                   |get_or_insert_ctor_field,   |get_or_insert_ctor_field,
                   |at cp/constexpr.c:3571      |at cp/constexpr.c:3571
                   |                            |since
                   |                            |r11-7980-gc3d3bb0f03dbd025
     Ever confirmed|0                           |1

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Confirmed, started with r11-7980-gc3d3bb0f03dbd025.

[Bug c++/101040] [11/12 Regression] Internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3571 since r11-7980-gc3d3bb0f03dbd025

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101040

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org

[Bug c++/101040] [11/12 Regression] Internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3571 since r11-7980-gc3d3bb0f03dbd025

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101040

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:2168bfb81448ae1bfa4351760a23d4ec051c2a00

commit r12-1827-g2168bfb81448ae1bfa4351760a23d4ec051c2a00
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Jun 24 17:32:02 2021 -0400

    c++: constexpr aggr init of empty class [PR101040]

    This is basically the aggregate initializer version of PR97566; as in that
    bug, we are trying to initialize empty field 'obj' in 'single' when there's
    no CONSTRUCTOR entry for the 'single' base class subobject of 'derived'. 
As
    with that bug, the fix is to stop trying to add entries for empty fields,
    this time in cxx_eval_bare_aggregate.

    The change to the other function isn't necessary for this version of
    the patch, but seems worthwhile for robustness anyway.

            PR c++/101040
            PR c++/97566

    gcc/cp/ChangeLog:

            * class.c (is_empty_field): Handle null argument.
            * constexpr.c (cxx_eval_bare_aggregate): Discard initializer
            for empty field.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/no_unique_address13.C: New test.

[Bug c++/101040] [11/12 Regression] Internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3571 since r11-7980-gc3d3bb0f03dbd025

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101040

--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> ---
Created attachment 51060
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51060&action=edit
bits dropped from the patch

putting these here in case I want them later.

[Bug c++/101040] [11/12 Regression] Internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3571 since r11-7980-gc3d3bb0f03dbd025

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101040

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:38fed4dfa25ac4894546f0589340ebfc5eef3bee

commit r11-8704-g38fed4dfa25ac4894546f0589340ebfc5eef3bee
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Jun 24 17:32:02 2021 -0400

    c++: constexpr aggr init of empty class [PR101040]

    This is basically the aggregate initializer version of PR97566; as in that
    bug, we are trying to initialize empty field 'obj' in 'single' when there's
    no CONSTRUCTOR entry for the 'single' base class subobject of 'derived'. 
As
    with that bug, the fix is to stop trying to add entries for empty fields,
    this time in cxx_eval_bare_aggregate.

    The change to the other function isn't necessary for this version of
    the patch, but seems worthwhile for robustness anyway.

            PR c++/101040
            PR c++/97566

    gcc/cp/ChangeLog:

            * class.c (is_empty_field): Handle null argument.
            * constexpr.c (cxx_eval_bare_aggregate): Discard initializer
            for empty field.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/no_unique_address13.C: New test.

[Bug c++/101040] [11/12 Regression] Internal compiler error: in get_or_insert_ctor_field, at cp/constexpr.c:3571 since r11-7980-gc3d3bb0f03dbd025

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101040

Jason Merrill <jason at gcc dot gnu.org> changed:

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

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for 11.2/12.