[Bug c++/106259] New: ICE in diag_mismatched_tags, at cp/parser.cc:33896

[Bug c++/106259] New: ICE in diag_mismatched_tags, at cp/parser.cc:33896

[gscfq@t-online.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

            Bug ID: 106259
           Summary: ICE in diag_mismatched_tags, at cp/parser.cc:33896
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gscfq@t-online.de
  Target Milestone: ---

Started with r10 and file g++.dg/template/dependent-name11.C :


$ gcc-13-20220710 -c dependent-name11.C -Wmismatched-tags
dependent-name11.C:15:1: internal compiler error: in diag_mismatched_tags, at
cp/parser.cc:33896
   15 | }
      | ^
0x904c4d class_decl_loc_t::diag_mismatched_tags(tree_node*)
        ../../gcc/cp/parser.cc:33896
0x90b465 class_decl_loc_t::diag_mismatched_tags()
        ../../gcc/cp/parser.cc:34018
0x9550cd c_parse_file()
        ../../gcc/cp/parser.cc:48482
0xae8181 c_common_parse_file()
        ../../gcc/c-family/c-opts.cc:1235

[Bug c++/106259] [10/11/12/13 Regression] ICE in diag_mismatched_tags, at cp/parser.cc:33896

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|ICE in                      |[10/11/12/13 Regression]
                   |diag_mismatched_tags, at    |ICE in
                   |cp/parser.cc:33896          |diag_mismatched_tags, at
                   |                            |cp/parser.cc:33896
   Target Milestone|---                         |10.5
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
                 CC|                            |mpolacek at gcc dot gnu.org,
                   |                            |msebor at gcc dot gnu.org
           Priority|P3                          |P2
   Last reconfirmed|                            |2022-07-11

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed.

commit 04dd734b52de121853e1ea6b3c197a598b294e23
Author: Martin Sebor <msebor@gmail.com>
Date:   Fri Mar 27 12:07:45 2020 -0400

    c++: avoid -Wredundant-tags on a first declaration in use [PR 93824]

[Bug c++/106259] [10/11/12/13 Regression] ICE in diag_mismatched_tags, at cp/parser.cc:33896

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Looks like
struct A<int>::W<U>
isn't in the class2loc hash table so we crash here:

33894       tree spec = specialization_of (type);
33895       cdlguide = class2loc.get (spec);
33896       gcc_assert (cdlguide != NULL);

[Bug c++/106259] [10/11/12/13 Regression] ICE in diag_mismatched_tags, at cp/parser.cc:33896

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
// PR c++/106259
// { dg-do compile { target c++11 } }

template<typename T> struct A {
  template<typename U>
  struct W { };
};

template<>
struct A<char> {
  template<typename U>
  class W { };
};

void
g ()
{
  struct A<char>::W<int> w1; // warn
  struct A<int>::W<int> w2; // dont warn
  class A<char>::W<int> w3; // dont warn
  class A<int>::W<int> w4; // warn
}

[Bug c++/106259] [10/11/12/13 Regression] ICE in diag_mismatched_tags, at cp/parser.cc:33896

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I know, in principle, how to fix it, but currently I'm struggling with getting
struct A<T>::W<U>
from
struct A<int>::W<U>

That we haven't found struct A<int>::W<U> in class2loc is actually OK, we don't
have a A<int> specialization, so we should see if W in the primary template A
was defined with class or struct.

[Bug c++/106259] [10/11/12/13 Regression] ICE in diag_mismatched_tags, at cp/parser.cc:33896

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

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

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Ah, this does what I want:

--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -34473,6 +34473,12 @@ class_decl_loc_t::diag_mismatched_tags (tree
type_decl)
     be (and inevitably is) at index zero.  */
       tree spec = specialization_of (type);
       cdlguide = class2loc.get (spec);
+      if (!cdlguide)
+   {
+     spec = most_general_template (spec);
+     spec = TYPE_MAIN_DECL (TREE_TYPE (spec));
+     cdlguide = class2loc.get (spec);
+   }
       gcc_assert (cdlguide != NULL);
     }
   else

[Bug c++/106259] [10/11/12/13 Regression] ICE in diag_mismatched_tags, at cp/parser.cc:33896

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

--- 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:71afd0628419c5d670701cb35bc9860380c7d9fb

commit r13-6417-g71afd0628419c5d670701cb35bc9860380c7d9fb
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Mar 1 14:28:46 2023 -0500

    c++: ICE with -Wmismatched-tags and member template [PR106259]

    -Wmismatched-tags warns about the (harmless) struct/class mismatch.
    For, e.g.,

      template<typename T> struct A { };
      class A<int> a;

    it works by adding A<T> to the class2loc hash table while parsing the
    class-head and then, while parsing the elaborate type-specifier, we
    add A<int>.  At the end of c_parse_file we go through the table and
    warn about the class-key mismatches.  In this PR we crash though; we
    have

      template<typename T> struct A {
        template<typename U> struct W { };
      };
      struct A<int>::W<int> w; // #1

    where while parsing A and #1 we've stashed
       A<T>
       A<T>::W<U>
       A<int>::W<int>
    into class2loc.  Then in class_decl_loc_t::diag_mismatched_tags TYPE
    is A<int>::W<int>, and specialization_of gets us A<int>::W<U>, which
    is not in class2loc, so we crash on gcc_assert (cdlguide).  But it's
    OK not to have found A<int>::W<U>, we should just look one "level" up,
    that is, A<T>::W<U>.

    It's important to handle class specializations, so e.g.

      template<>
      struct A<char> {
        template<typename U>
        class W { };
      };

    where W's class-key is different than in the primary template above,
    so we should warn depending on whether we're looking into A<char>
    or into a different instantiation.

            PR c++/106259

    gcc/cp/ChangeLog:

            * parser.cc (class_decl_loc_t::diag_mismatched_tags): If the first
            lookup of SPEC didn't find anything, try to look for
            most_general_template.

    gcc/testsuite/ChangeLog:

            * g++.dg/warn/Wmismatched-tags-11.C: New test.

[Bug c++/106259] [10/11/12 Regression] ICE in diag_mismatched_tags, at cp/parser.cc:33896

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[10/11/12/13 Regression]    |[10/11/12 Regression] ICE
                   |ICE in                      |in diag_mismatched_tags, at
                   |diag_mismatched_tags, at    |cp/parser.cc:33896
                   |cp/parser.cc:33896          |

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

[Bug c++/106259] [10/11/12 Regression] ICE in diag_mismatched_tags, at cp/parser.cc:33896

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

--- Comment #8 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:3a2310d4b229e707bbc5440150bf180e0499273a

commit r12-9217-g3a2310d4b229e707bbc5440150bf180e0499273a
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Mar 1 14:28:46 2023 -0500

    c++: ICE with -Wmismatched-tags and member template [PR106259]

    -Wmismatched-tags warns about the (harmless) struct/class mismatch.
    For, e.g.,

      template<typename T> struct A { };
      class A<int> a;

    it works by adding A<T> to the class2loc hash table while parsing the
    class-head and then, while parsing the elaborate type-specifier, we
    add A<int>.  At the end of c_parse_file we go through the table and
    warn about the class-key mismatches.  In this PR we crash though; we
    have

      template<typename T> struct A {
        template<typename U> struct W { };
      };
      struct A<int>::W<int> w; // #1

    where while parsing A and #1 we've stashed
       A<T>
       A<T>::W<U>
       A<int>::W<int>
    into class2loc.  Then in class_decl_loc_t::diag_mismatched_tags TYPE
    is A<int>::W<int>, and specialization_of gets us A<int>::W<U>, which
    is not in class2loc, so we crash on gcc_assert (cdlguide).  But it's
    OK not to have found A<int>::W<U>, we should just look one "level" up,
    that is, A<T>::W<U>.

    It's important to handle class specializations, so e.g.

      template<>
      struct A<char> {
        template<typename U>
        class W { };
      };

    where W's class-key is different than in the primary template above,
    so we should warn depending on whether we're looking into A<char>
    or into a different instantiation.

            PR c++/106259

    gcc/cp/ChangeLog:

            * parser.cc (class_decl_loc_t::diag_mismatched_tags): If the first
            lookup of SPEC didn't find anything, try to look for
            most_general_template.

    gcc/testsuite/ChangeLog:

            * g++.dg/warn/Wmismatched-tags-11.C: New test.

    (cherry picked from commit 71afd0628419c5d670701cb35bc9860380c7d9fb)

[Bug c++/106259] [10/11 Regression] ICE in diag_mismatched_tags, at cp/parser.cc:33896

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
            Summary|[10/11/12 Regression] ICE   |[10/11 Regression] ICE in
                   |in diag_mismatched_tags, at |diag_mismatched_tags, at
                   |cp/parser.cc:33896          |cp/parser.cc:33896

--- Comment #9 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.