[Bug c++/101073] New: [9/10/11/12 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[Bug c++/101073] New: [9/10/11/12 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[gscfq@t-online.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

            Bug ID: 101073
           Summary: [9/10/11/12 Regression] ICE in
                    cxx_eval_constant_expression, at cp/constexpr.c:6941
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gscfq@t-online.de
  Target Milestone: ---

With file gcc/testsuite/g++.dg/cpp1y/constexpr-nsdmi9.C and option
-fno-elide-constructors, affects versions down to r6 :


$ g++-12-20210613 -c constexpr-nsdmi9.C -fno-elide-constructors
constexpr-nsdmi9.C:15:19: internal compiler error: in
cxx_eval_constant_expression, at cp/constexpr.c:6941
   15 | constexpr X o = { };
      |                   ^
0x6fae2c cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6941
0x6fa62e cxx_eval_indirect_ref
        ../../gcc/cp/constexpr.c:5019
0x6fa62e cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6461
0x6fa4b2 cxx_eval_component_reference
        ../../gcc/cp/constexpr.c:3879
0x6fa4b2 cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6637
0x6fa62e cxx_eval_indirect_ref
        ../../gcc/cp/constexpr.c:5019
0x6fa62e cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6461
0x7009eb cxx_eval_store_expression
        ../../gcc/cp/constexpr.c:5327
0x6fa70d cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6350
0x6f7344 cxx_eval_call_expression
        ../../gcc/cp/constexpr.c:2539
0x6f9ff0 cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6241
0x6f8fe9 cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6733
0x6f8fe9 cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6733
0x6f8fe9 cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6733
0x6faff0 cxx_eval_indirect_ref
        ../../gcc/cp/constexpr.c:4976
0x6faff0 cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6461
0x70075f cxx_eval_store_expression
        ../../gcc/cp/constexpr.c:5263
0x6fa70d cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6350
0x6f7344 cxx_eval_call_expression
        ../../gcc/cp/constexpr.c:2539
0x6f9ff0 cxx_eval_constant_expression
        ../../gcc/cp/constexpr.c:6241

[Bug c++/101073] [9/10/11/12 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |9.5

[Bug c++/101073] [9/10/11/12 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-10-02
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

[Bug c++/101073] [9/10/11/12 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |jason at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started to ICE with r6-7530-g86461cad6f7b751c19fb96fefc62d8e119c8a351 , before
that it has been rejected.

[Bug c++/101073] [10/11/12/13 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|9.5                         |10.4

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 9 branch is being closed

[Bug c++/101073] [10/11/12/13 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.4                        |10.5

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 10.4 is being released, retargeting bugs to GCC 10.5.

[Bug c++/101073] [10/11/12/13 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
A similar test that doesn't use op=:

struct Y
{
  int a;
};

struct X
{
  Y b = Y{1};
  Y c = this->b;
};

constexpr X o = { };
static_assert(o.b.a == 1 && o.c.a == 1, "");

[Bug c++/101073] [10/11/12/13 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

[Bug c++/101073] [10/11/12/13 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:b2287a4d9a640fdc2caef6a067830ea65044deb7

commit r13-6145-gb2287a4d9a640fdc2caef6a067830ea65044deb7
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Feb 8 19:13:18 2023 -0500

    c++: ICE with -fno-elide-constructors and trivial fn [PR101073]

    In constexpr-nsdmi3.C, with -fno-elide-constructors, we don't elide
    the Y::Y(const Y&) call used to initialize o.c.  So store_init_value
    -> cxx_constant_init must constexpr-evaluate the call to Y::Y(const Y&)
    in cxx_eval_call_expression.  It's a trivial function, so we do the
    "Shortcut trivial constructor/op=" code and rather than evaluating
    the function, we just create an assignment

      o.c = *(const struct Y &) (const struct Y *) &(&<PLACEHOLDER_EXPR struct
X>)->b

    which is a MODIFY_EXPR, so the preeval code in cxx_eval_store_expression
    clears .ctor and .object, therefore we can't replace the PLACEHOLDER_EXPR
    whereupon we crash at

          /* A placeholder without a referent.  We can get here when
             checking whether NSDMIs are noexcept, or in massage_init_elt;
             just say it's non-constant for now.  */
          gcc_assert (ctx->quiet);

    The PLACEHOLDER_EXPR can also be on the LHS as in constexpr-nsdmi10.C.
    I don't think we can do much here, but I noticed that the whole
    trivial_fn_p (fun) block is only entered when -fno-elide-constructors.
    This is true since GCC 9; it wasn't easy to bisect what changes made it
    so, but r240845 is probably one of them.  -fno-elide-constructors is an
    option for experiments only so it's not clear to me why we'd still want
    to shortcut trivial constructor/op=.  I propose to remove the code and
    add a checking assert to make sure we're not getting a trivial_fn_p
    unless -fno-elide-constructors.

            PR c++/101073

    gcc/cp/ChangeLog:

            * constexpr.cc (cxx_eval_call_expression): Replace shortcutting
trivial
            constructor/op= with a checking assert.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp0x/constexpr-nsdmi3.C: New test.
            * g++.dg/cpp1y/constexpr-nsdmi10.C: New test.

[Bug c++/101073] [10/11/12/13 Regression] ICE in cxx_eval_constant_expression, at cp/constexpr.c:6941

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101073

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed for GCC 13, not backporting.