[Bug c++/108179] New: [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[Bug c++/108179] New: [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[s at stu dot scot]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

            Bug ID: 108179
           Summary: [11/12 regression] ICE related to template template
                    parameters in tsubst, at cp/pt.cc:15782
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: s at stu dot scot
  Target Milestone: ---

Created attachment 54126
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54126&action=edit
Bug report from -freport-bug

The following code produces an internal compiler error on all g++ 11 and 12
versions I tried. This is the most minimal example I could come up with. It
compiles fine under g++ 10 and clang.

```
template <class T, T X, template <T> class F>
struct Foo {};

template <class T0, class T1, T1 X, template <T1> class F>
void f(Foo<T1, X, F>) {}
```

Works in:
* g++-10 (Ubuntu 10.4.0-4ubuntu1~22.04) 10.4.0
Doesn't work in:
* g++-11 (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
* g++-12 (Ubuntu 12.1.0-2ubuntu1~22.04) 12.1.0
* x86-64 gcc 12.2 on compiler explorer: https://godbolt.org/z/EMncPKcea

[Bug c++/108179] [11/12/13 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.4
      Known to fail|                            |11.3.0, 12.1.0
      Known to work|                            |11.1.0, 11.2.0
            Summary|[11/12 regression] ICE      |[11/12/13 regression] ICE
                   |related to template         |related to template
                   |template parameters in      |template parameters in
                   |tsubst, at cp/pt.cc:15782   |tsubst, at cp/pt.cc:15782

[Bug c++/108179] [11/12/13 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-12-19
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

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

[Bug c++/108179] [11/12/13 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/108179] [11/12/13 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org,
                   |                            |ppalka at gcc dot gnu.org
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=104107
           Keywords|needs-bisection             |

--- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Started with r12-7236-g2c3309e3d0f5cb

[Bug c++/108179] [11/12/13 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

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

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

[Bug c++/108179] [11/12/13 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:5ccbf162511b896672a72934c3cafd37a42d6438

commit r13-6692-g5ccbf162511b896672a72934c3cafd37a42d6438
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Mar 14 22:07:45 2023 -0400

    c++: coerce_template_template_parms interface tweak

    This should have no semantic effect, but is a prerequisite for the PR108179
    fix to follow.

            PR c++/108179

    gcc/cp/ChangeLog:

            * pt.cc (coerce_template_template_parms): Take the arg and parm
            templates directly.
            (coerce_template_template_parm): Adjust.
            (template_template_parm_bindings_ok_p): Adjust.
            (convert_template_argument): Adjust.

[Bug c++/108179] [11/12/13 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

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

https://gcc.gnu.org/g:3ea64aad06a2b32739028bae03b9b9a5691d2d30

commit r13-6693-g3ea64aad06a2b32739028bae03b9b9a5691d2d30
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Mar 10 14:55:27 2023 -0500

    c++: passing one ttp to another [PR108179]

    I kept trying to improve our choice of how many levels of outer_args to
add,
    when really the problem was that outer_args are for PARM and for this
    reverse deduction we should be adding the outer arguments for ARG.

    I spent quite a while trying to get DECL_CONTEXT set consistently on
    template template parameters that have gone through
    reduce_template_parm_level before I realized I could just use
    current_scope().

            PR c++/108179
            PR c++/104107
            PR c++/95036

    gcc/cp/ChangeLog:

            * pt.cc (coerce_template_template_parms): Use args from
            DECL_CONTEXT (arg_tmpl) instead of outer_args.

    gcc/testsuite/ChangeLog:

            * g++.dg/template/ttp35.C: New test.

[Bug c++/108179] [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[11/12/13 regression] ICE   |[11/12 regression] ICE
                   |related to template         |related to template
                   |template parameters in      |template parameters in
                   |tsubst, at cp/pt.cc:15782   |tsubst, at cp/pt.cc:15782

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for 13 so far.

[Bug c++/108179] [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[s at stu dot scot]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

--- Comment #6 from stu t <s at stu dot scot> ---
Thank you for looking into this! :)

[Bug c++/108179] [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to stu t from comment #6)
> Thank you for looking into this! :)

You're welcome!  I'm currently leaning toward backporting this to 12.4 rather
than 12.3, but am interested in your thoughts.

[Bug c++/108179] [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.4                        |11.5

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 11.4 is being released, retargeting bugs to GCC 11.5.

[Bug c++/108179] [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> ---
This patch caused PR110566.

[Bug c++/108179] [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:b3adcc60dcf3314f47f5409aecef40607f82b80b

commit r14-2809-gb3adcc60dcf3314f47f5409aecef40607f82b80b
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Jul 26 17:21:26 2023 -0400

    c++: passing partially inst tmpl as ttp [PR110566]

    Since the template arguments 'pargs' we pass to coerce_template_parms from
    coerce_template_template_parms are always a full set, we need to make sure
    we always pass the parameters of the most general template because if the
    template is partially instantiated then the levels won't match up.  In the
    testcase below during said call to coerce_template_parms the parameters are
    {X, Y}, both level 1 rather than 2, and the arguments are {{int}, {N, M}},
    which results in a crash during auto deduction for parameters' types.

            PR c++/110566
            PR c++/108179

    gcc/cp/ChangeLog:

            * pt.cc (coerce_template_template_parms): Simplify by using
            DECL_INNERMOST_TEMPLATE_PARMS and removing redundant asserts.
            Always pass the parameters of the most general template to
            coerce_template_parms.

    gcc/testsuite/ChangeLog:

            * g++.dg/template/ttp38.C: New test.

[Bug c++/108179] [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:b8218eb2266811991b8163f36d5c1d974cb50b93

commit r14-2810-gb8218eb2266811991b8163f36d5c1d974cb50b93
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Jul 26 17:21:43 2023 -0400

    c++: passing partially inst ttp as ttp [PR110566]

    The previous fix doesn't work for partially instantiated ttps mainly
    because most_general_template is a no-op for them.  This patch fixes
    this by giving such ttps a DECL_TEMPLATE_INFO (extending the
    r11-734-g2fb595f8348e16 fix) with which most_general_template can obtain
    the original, unlowered ttp.

    This patch additionally makes coerce_template_template_parms use the
    correct amount of levels from the scope of a ttp argument.

            PR c++/110566
            PR c++/108179

    gcc/cp/ChangeLog:

            * pt.cc (reduce_template_parm_level): Set DECL_TEMPLATE_INFO
            on the DECL_TEMPLATE_RESULT of the new ttp.
            (add_defaults_to_ttp): Make a copy of the original ttp's
            DECL_TEMPLATE_RESULT, and update this copy's DECL_TEMPLATE_INFO
            as well.
            (coerce_template_template_parms): Make sure 'scope_args' has
            the right amount of levels for the ttp argument.
            (most_general_template): Handle template template parameters.
            (rewrite_template_parm): Set DECL_TEMPLATE_RESULT on the
            DECL_TEMPLATE_RESULT of the new ttp.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1z/class-deduction115.C: New test.
            * g++.dg/template/ttp39.C: New test.

[Bug c++/108179] [11/12 regression] ICE related to template template parameters in tsubst, at cp/pt.cc:15782

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108179

--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:2c6e76ff039782401f705cacda60c11f8dfac3b1

commit r13-7692-g2c6e76ff039782401f705cacda60c11f8dfac3b1
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Jul 26 17:21:26 2023 -0400

    c++: passing partially inst tmpl as ttp [PR110566]

    Since the template arguments 'pargs' we pass to coerce_template_parms from
    coerce_template_template_parms are always a full set, we need to make sure
    we always pass the parameters of the most general template because if the
    template is partially instantiated then the levels won't match up.  In the
    testcase below during said call to coerce_template_parms the parameters are
    {X, Y}, both level 1 rather than 2, and the arguments are {{int}, {N, M}},
    which results in a crash during auto deduction for parameters' types.

            PR c++/110566
            PR c++/108179

    gcc/cp/ChangeLog:

            * pt.cc (coerce_template_template_parms): Simplify by using
            DECL_INNERMOST_TEMPLATE_PARMS and removing redundant asserts.
            Always pass the parameters of the most general template to
            coerce_template_parms.

    gcc/testsuite/ChangeLog:

            * g++.dg/template/ttp38.C: New test.

    (cherry picked from commit b3adcc60dcf3314f47f5409aecef40607f82b80b)