From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id DB1883861812; Sun,  7 Feb 2021 22:35:33 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org DB1883861812
From: "david at doublewise dot net" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/98990] New: Internal compiler error when two overloaded
 functions return `auto &&` and one accepts an `auto` parameter
Date: Sun, 07 Feb 2021 22:35:33 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 11.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: david at doublewise dot net
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-98990-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Sun, 07 Feb 2021 22:35:34 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98990

            Bug ID: 98990
           Summary: Internal compiler error when two overloaded functions
                    return `auto &&` and one accepts an `auto` parameter
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david at doublewise dot net
  Target Milestone: ---

The following valid translation unit

```
constexpr int x =3D 0;

constexpr auto && f() {
        return x;
}
constexpr auto && f(auto) {
        return x;
}
```

causes gcc to crash with

```
<source>:6:25: internal compiler error: same canonical type node for differ=
ent
types 'auto&&' and 'auto&&'
    6 | constexpr auto && f(auto) {
      |                         ^
0x1ce6f09 internal_error(char const*, ...)
        ???:0
0x9c60ce comptypes(tree_node*, tree_node*, int)
        ???:0
0x78ef77 decls_match(tree_node*, tree_node*, bool)
        ???:0
0x7c003c cplus_decl_attributes(tree_node**, tree_node*, int)
        ???:0
0x79f277 grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
        ???:0
0x7a3916 start_function(cp_decl_specifier_seq*, cp_declarator const*,
tree_node*)
        ???:0
0x8de23d c_parse_file()
        ???:0
0xa5b7c2 c_common_parse_file()
        ???:0
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.
Compiler returned: 1
```

See it live: https://godbolt.org/z/bnszYo

This code was accepted in gcc 10.2, but it is rejected by the upcoming 11.0=
.=