[Bug c++/107938] New: ICE directly returning `this` of `extern` variable in template

[Bug c++/107938] New: ICE directly returning `this` of `extern` variable in template

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

            Bug ID: 107938
           Summary: ICE directly returning `this` of `extern` variable in
                    template
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johelegp at gmail dot com
                CC: johelegp at gmail dot com
  Target Milestone: ---

See https://compiler-explorer.com/z/4d1esaber.

```C++
struct Q {
  int n;
  constexpr const Q* operator()(auto) const { return this; }
};

extern const Q q;

template<int>
constexpr const Q* p = q(0);
```

```
<source>:9:27: internal compiler error: Segmentation fault
    9 | constexpr const Q* p = q(0);
      |                           ^
0x22e3a9e internal_error(char const*, ...)
        ???:0
0xce2006 convert_for_initialization(tree_node*, tree_node*, tree_node*, int,
impl_conv_rhs, tree_node*, int, int)
        ???:0
0xced3f0 store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ???:0
0xb22845 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int)
        ???:0
0xc20997 c_parse_file()
        ???:0
0xd5b949 c_common_parse_file()
        ???:0
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1
```

Being less direct works: https://compiler-explorer.com/z/jn99aG36e.

[Bug c++/107938] [11/12/13 Regression] ICE directly returning `this` of `extern` variable in template

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.4
   Last reconfirmed|                            |2022-11-30
            Summary|ICE directly returning      |[11/12/13 Regression] ICE
                   |`this` of `extern` variable |directly returning `this`
                   |in template                 |of `extern` variable in
                   |                            |template
      Known to work|                            |10.4.0
     Ever confirmed|0                           |1
           Keywords|                            |needs-bisection
             Status|UNCONFIRMED                 |NEW
      Known to fail|                            |11.1.0

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed. A regression from GCC 10.4.0.

A C++14 testcase (removing the auto from the operator()):
```
struct Q {
  int n;
  constexpr const Q* operator()(int) const { return this; }
};

extern const Q q;

template<int>
constexpr const Q* p = q(0);
```

[Bug c++/107938] [11/12/13 Regression] ICE directly returning `this` of `extern` variable in template

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Hmm, the following slightly modified testcase works in GCC 8.5.0 but started to
ICE in GCC 9.1.0:
```
struct Q {
  int n;
  constexpr const Q* operator()(int) const { return this; }
};

constexpr Q q{};

template<int>
constexpr const Q* p = q(0);
```

It is still a regression though.

[Bug c++/107938] [11/12/13 Regression] ICE directly returning `this` of `extern` variable in template

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

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

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

[Bug c++/107938] [11/12/13 Regression] ICE directly returning `this` of `extern` variable in template since r11-557

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[11/12/13 Regression] ICE   |[11/12/13 Regression] ICE
                   |directly returning `this`   |directly returning `this`
                   |of `extern` variable in     |of `extern` variable in
                   |template                    |template since r11-557
           Keywords|needs-bisection             |
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |jason at gcc dot gnu.org,
                   |                            |ppalka at gcc dot gnu.org

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
This also started with r11-557-gbeb019d346b903c16b9fd349937de444b6a8b6c0

[Bug c++/107938] [11/12/13 Regression] ICE directly returning `this` of `extern` variable in template since r11-557

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

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

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

[Bug c++/107938] [11/12/13 Regression] ICE directly returning `this` of `extern` variable in template since r11-557

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Patch posted:
<https://gcc.gnu.org/pipermail/gcc-patches/2023-February/612700.html>

[Bug c++/107938] [11/12/13 Regression] ICE directly returning `this` of `extern` variable in template since r11-557

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

--- Comment #5 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:ea718febab2a1f6e58806738abf70f1c73c6a308

commit r13-6376-gea718febab2a1f6e58806738abf70f1c73c6a308
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Feb 23 17:54:47 2023 -0500

    c++: ICE with constexpr variable template [PR107938]

    Since r11-557, cp_finish_decl can call check_initializer even in
    a template for a constexpr initializer.  That ultimately leads to
    convert_for_assignment and check_address_or_pointer_of_packed_member,
    where we crash, because it doesn't expect that the CALL_EXPR is
    a function object.  Q has a constexpr operator(), but since we're
    in a template, q(0) is a CALL_EXPR whose CALL_EXPR_FN is just
    a VAR_DECL; it hasn't been converted to Q::operator<int>(&q, 0) yet.
    I propose to robustify check_address_or_pointer_of_packed_member.

    var-templ74.C has an XFAIL, subject to 107939.

    I noticed that our -Waddress-of-packed-member tests weren't testing
    member functions, added thus.  (I was tempted to check
    FUNCTION_POINTER_TYPE_P but that doesn't include METHOD_TYPE.)

            PR c++/107938

    gcc/c-family/ChangeLog:

            * c-warn.cc (check_address_or_pointer_of_packed_member): Check
            POINTER_TYPE_P.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1y/var-templ73.C: New test.
            * g++.dg/cpp1y/var-templ74.C: New test.
            * g++.dg/warn/Waddress-of-packed-member3.C: New test.

[Bug c++/107938] [11/12 Regression] ICE directly returning `this` of `extern` variable in template since r11-557

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Marek Polacek
<mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:445082ff3cb7f9d30021adf338e9ab6038c3e412

commit r12-9215-g445082ff3cb7f9d30021adf338e9ab6038c3e412
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Feb 23 17:54:47 2023 -0500

    c++: ICE with constexpr variable template [PR107938]

    Since r11-557, cp_finish_decl can call check_initializer even in
    a template for a constexpr initializer.  That ultimately leads to
    convert_for_assignment and check_address_or_pointer_of_packed_member,
    where we crash, because it doesn't expect that the CALL_EXPR is
    a function object.  Q has a constexpr operator(), but since we're
    in a template, q(0) is a CALL_EXPR whose CALL_EXPR_FN is just
    a VAR_DECL; it hasn't been converted to Q::operator<int>(&q, 0) yet.
    I propose to robustify check_address_or_pointer_of_packed_member.

    var-templ74.C has an XFAIL, subject to 107939.

    I noticed that our -Waddress-of-packed-member tests weren't testing
    member functions, added thus.  (I was tempted to check
    FUNCTION_POINTER_TYPE_P but that doesn't include METHOD_TYPE.)

            PR c++/107938

    gcc/c-family/ChangeLog:

            * c-warn.cc (check_address_or_pointer_of_packed_member): Check
            POINTER_TYPE_P.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1y/var-templ73.C: New test.
            * g++.dg/cpp1y/var-templ74.C: New test.
            * g++.dg/warn/Waddress-of-packed-member3.C: New test.

    (cherry picked from commit ea718febab2a1f6e58806738abf70f1c73c6a308)

[Bug c++/107938] [11/12 Regression] ICE directly returning `this` of `extern` variable in template since r11-557

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107938

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

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

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.