[Bug c++/95820] New: ICE in splice_late_return_type, at cp/pt.c:29034

[Bug c++/95820] New: ICE in splice_late_return_type, at cp/pt.c:29034

[haoxintu at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

            Bug ID: 95820
           Summary: ICE in splice_late_return_type, at cp/pt.c:29034
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: ice-on-invalid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: haoxintu at gmail dot com
  Target Milestone: ---

This case bug.cc, reduced by C-Reduce, crashed GCC.

$cat bug.cc
constexpr (*a)()->bool,

$g++ -w -fpermissive small.cc
bug.cc:1:19: internal compiler error: in splice_late_return_type, at
cp/pt.c:29034
    1 | constexpr (*a)()->bool,
      |                   ^~~~
0x5cd1f6 splice_late_return_type(tree_node*, tree_node*)
        ../../gcc/cp/pt.c:29034
0x67db9a grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
        ../../gcc/cp/decl.c:12154
0x684228 start_decl(cp_declarator const*, cp_decl_specifier_seq*, int,
tree_node*, tree_node*, tree_node**)
        ../../gcc/cp/decl.c:5231
0x70c8ce cp_parser_init_declarator
        ../../gcc/cp/parser.c:20817
0x6efcc2 cp_parser_simple_declaration
        ../../gcc/cp/parser.c:13785
0x7159c6 cp_parser_declaration
        ../../gcc/cp/parser.c:13484
0x7160b4 cp_parser_translation_unit
        ../../gcc/cp/parser.c:4761
0x7160b4 c_parse_file()
        ../../gcc/cp/parser.c:44034
0x7de74b c_common_parse_file()
        ../../gcc/c-family/c-opts.c:1190
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

My GCC version is
$g++ --version
g++ (GCC) 11.0.0 20200605 (experimental)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[Bug c++/95820] ICE in splice_late_return_type, at cp/pt.c:29034

[haoxintu at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

--- Comment #1 from Haoxin Tu <haoxintu at gmail dot com> ---
(In reply to Haoxin Tu from comment #0)

> $g++ -w -fpermissive small.cc

Here is a mistake, and it should be

$g++ -w -fpermissive bug.cc

[Bug c++/95820] ICE in splice_late_return_type, at cp/pt.c:29034

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-06-22
             Status|UNCONFIRMED                 |NEW
                 CC|                            |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed.

[Bug c++/95820] ICE in splice_late_return_type, at cp/pt.c:29034

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Hit this when reducing something:

template class a b[]()->int

So it'd be nice to fix it to alleviate problems when reducing C++ code.

[Bug c++/95820] [10/11 Regression] ICE in splice_late_return_type, at cp/pt.c:29034

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|ICE in                      |[10/11 Regression] ICE in
                   |splice_late_return_type, at |splice_late_return_type, at
                   |cp/pt.c:29034               |cp/pt.c:29034
   Target Milestone|---                         |10.2

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started with r10-6571-ga6ee556c7659877bb59b719f11ca2153e86ded59

[Bug c++/95820] [10/11 Regression] ICE in splice_late_return_type, at cp/pt.c:29034

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

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++/95820] [10/11 Regression] ICE in splice_late_return_type, at cp/pt.c:29034

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
*** Bug 95936 has been marked as a duplicate of this bug. ***

[Bug c++/95820] [10/11 Regression] ICE in splice_late_return_type, at cp/pt.c:29034

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

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

https://gcc.gnu.org/g:9eb370f19c1198e62d47eae74531e54d0b098bf1

commit r11-2085-g9eb370f19c1198e62d47eae74531e54d0b098bf1
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Jun 24 17:39:21 2020 -0400

    c++: Improve checking of decls with trailing return type [PR95820]

    This is an ICE-on-invalid but I've been seeing it when reducing
    various testcases, so it's more important for me than usually.

    splice_late_return_type now checks that if we've seen a late return
    type, the function return type was auto.  That's a fair assumption
    but grokdeclarator/cdk_function wasn't giving errors for function
    pointers and similar.  So we want to perform various checks not only
    when funcdecl_p || inner_declarator == NULL.  But only give the
    !late_return_type errors when funcdecl_p, to accept e.g.

    auto (*fp)() = f;

    in C++11.  Here's a diff -w to ease the review:

    --- a/gcc/cp/decl.c
    +++ b/gcc/cp/decl.c
    @@ -12102,14 +12102,9 @@ grokdeclarator (const cp_declarator *declarator,

                /* Handle a late-specified return type.  */
                tree late_return_type =
declarator->u.function.late_return_type;
    -           if (funcdecl_p
    -               /* This is the case e.g. for
    -                  using T = auto () -> int.  */
    -               || inner_declarator == NULL)
    -             {
                if (tree auto_node = type_uses_auto (type))
                  {
    -                   if (!late_return_type)
    +               if (!late_return_type && funcdecl_p)
                      {
                        if (current_class_type
                            && LAMBDA_TYPE_P (current_class_type))
    @@ -12201,7 +12196,6 @@ grokdeclarator (const cp_declarator *declarator,
                                "type specifier", name);
                    return error_mark_node;
                  }
    -             }
                type = splice_late_return_type (type, late_return_type);
                if (type == error_mark_node)
                  return error_mark_node;

    gcc/cp/ChangeLog:

            PR c++/95820
            * decl.c (grokdeclarator) <case cdk_function>: Check also
            pointers/references/... to functions.

    gcc/testsuite/ChangeLog:

            PR c++/95820
            * g++.dg/cpp1y/auto-fn58.C: New test.

[Bug c++/95820] [10 Regression] ICE in splice_late_return_type, at cp/pt.c:29034

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[10/11 Regression] ICE in   |[10 Regression] ICE in
                   |splice_late_return_type, at |splice_late_return_type, at
                   |cp/pt.c:29034               |cp/pt.c:29034
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed in GCC 11.

[Bug c++/95820] [10 Regression] ICE in splice_late_return_type, at cp/pt.c:29034

[slyfox at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

Sergei Trofimovich <slyfox at gcc dot gnu.org> changed:

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

--- Comment #8 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
In https://bugs.gentoo.org/730406 we see it on gcc-10.2.0 as well. Minimal
example:

$ cat a.cc
template <long()()->decltype(0)
$ LANG=C gcc-10.2.0 a.cc
a.cc:1:21: internal compiler error: in splice_late_return_type, at
cp/pt.c:29152

Should it be backported to gcc-10?

[Bug c++/95820] [10 Regression] ICE in splice_late_return_type, at cp/pt.c:29034

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

--- Comment #9 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
We usually don't backport fixed for ices-on-invalid but I could be convinced in
this case.

[Bug c++/95820] [10 Regression] ICE in splice_late_return_type, at cp/pt.c:29034

[slyfox at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95820

Sergei Trofimovich <slyfox at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.2                        |11.0

--- Comment #10 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
Oh, that makes sense. Adjusting the Target to 11.0.

I don't feel strongly about it either. We did not get reports until 10.2, so
maybe it's not that frequent.