[Bug libstdc++/101056] New: std::compare_partial_order_fallback missing the constraint of "F < E is well-formed"

[Bug libstdc++/101056] New: std::compare_partial_order_fallback missing the constraint of "F < E is well-formed"

[hewillk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101056

            Bug ID: 101056
           Summary: std::compare_partial_order_fallback missing the
                    constraint of "F < E is well-formed"
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

In [cmp#alg-6.3]: Otherwise, if the expressions E == F, E < F, and F < E are
all well-formed and convertible to bool, [...].

#include <compare>
struct E {};
const E e;
E f;
bool operator< (const E&, E&) { return false; }
bool operator==(const E&, E&) { return true; }
auto ord = std::compare_partial_order_fallback(e, f);

https://godbolt.org/z/TTooWPqEz

[Bug libstdc++/101056] std::compare_partial_order_fallback missing the constraint of "F < E is well-formed"

[hewillk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101056

--- Comment #1 from 康桓瑋 <hewillk at gmail dot com> ---
This is not a bug, it's just that LWG3465 has not been implemented yet.

[Bug libstdc++/101056] std::compare_partial_order_fallback missing the constraint of "F < E is well-formed"

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101056

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org
   Last reconfirmed|                            |2021-06-14
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1

[Bug libstdc++/101056] std::compare_partial_order_fallback missing the constraint of "F < E is well-formed"

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101056

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

https://gcc.gnu.org/g:b76a529c095f076c4780df0c913cf6d2391bcbc9

commit r12-1425-gb76a529c095f076c4780df0c913cf6d2391bcbc9
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Jun 14 12:30:52 2021 +0100

    libstdc++: Implement LWG 3465 for std::compare_partial_order_fallback
[PR101056]

    libstdc++-v3/ChangeLog:

            PR libstdc++/101056
            * libsupc++/compare (compare_partial_order_fallback): Add
            constraint using reversed parameter order, as per LWG 3465.
            * testsuite/18_support/comparisons/algorithms/fallback.cc:
            Adjust expected result.

[Bug libstdc++/101056] std::compare_partial_order_fallback missing the constraint of "F < E is well-formed"

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101056

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:546cf317558bfb178b7cadd346bb43cb963e9ce6

commit r11-8848-g546cf317558bfb178b7cadd346bb43cb963e9ce6
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Jun 14 12:30:52 2021 +0100

    libstdc++: Implement LWG 3465 for std::compare_partial_order_fallback
[PR101056]

    libstdc++-v3/ChangeLog:

            PR libstdc++/101056
            * libsupc++/compare (compare_partial_order_fallback): Add
            constraint using reversed parameter order, as per LWG 3465.
            * testsuite/18_support/comparisons/algorithms/fallback.cc:
            Adjust expected result.

    (cherry picked from commit b76a529c095f076c4780df0c913cf6d2391bcbc9)

[Bug libstdc++/101056] std::compare_partial_order_fallback missing the constraint of "F < E is well-formed"

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101056

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

https://gcc.gnu.org/g:452bfa3f41733eed6f07e5a8aae0bb8214cc6ce6

commit r10-10029-g452bfa3f41733eed6f07e5a8aae0bb8214cc6ce6
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Jun 14 12:30:52 2021 +0100

    libstdc++: Implement LWG 3465 for std::compare_partial_order_fallback
[PR101056]

    libstdc++-v3/ChangeLog:

            PR libstdc++/101056
            * libsupc++/compare (compare_partial_order_fallback): Add
            constraint using reversed parameter order, as per LWG 3465.
            * testsuite/18_support/comparisons/algorithms/fallback.cc:
            Adjust expected result.

    (cherry picked from commit b76a529c095f076c4780df0c913cf6d2391bcbc9)

[Bug libstdc++/101056] std::compare_partial_order_fallback missing the constraint of "F < E is well-formed"

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101056

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED
   Target Milestone|---                         |10.4

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 10.4 and 11.3

[Bug libstdc++/101056] std::compare_partial_order_fallback missing the constraint of "F < E is well-formed"

[clyon at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101056

Christophe Lyon <clyon at gcc dot gnu.org> changed:

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

--- Comment #6 from Christophe Lyon <clyon at gcc dot gnu.org> ---
On gcc-11, since r11-8848, I've noticed an ICE on arm-none-linux-gnueabi
(arm-none-linux-gnueabihf is OK):
FAIL: g++.dg/modules/xtreme-header-5_b.C -std=c++2b (internal compiler error)
FAIL: g++.dg/modules/xtreme-header-5_b.C -std=c++2b (test for excess errors)
Excess errors:
/gcc/testsuite/g++.dg/modules/xtreme-header-5_b.C:4:30: internal compiler
error: in add_mergeable_specialization, at cp/pt.c:30084
0x8b245f add_mergeable_specialization(bool, bool, spec_entry*, tree_node*,
unsigned int)
        /gcc/cp/pt.c:30084
0x81099a trees_in::decl_value()
        /gcc/cp/module.cc:8075
0x8123c7 trees_in::tree_node(bool)
        /gcc/cp/module.cc:9155
0x81aaeb module_state::read_cluster(unsigned int)
        /gcc/cp/module.cc:14813
0x81ae84 module_state::load_section(unsigned int, binding_slot*)
        /gcc/cp/module.cc:18084
0x81bde7 module_state::read_language(bool)
        /gcc/cp/module.cc:18013
0x81c0ba direct_import
        /gcc/cp/module.cc:18879
0x890a64 cp_parser_translation_unit
        /gcc/cp/parser.c:4907
0x890a64 c_parse_file()
        /gcc/cp/parser.c:45324
0xa101dc c_common_parse_file()
        /gcc/c-family/c-opts.c:1218

trunk and gcc-10 seem OK.