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 2BD5E3861971; Fri, 26 Feb 2021 12:29:16 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2BD5E3861971
From: "nickgray0 at brown dot edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/99287] New: std::source_location::function_name breaks
 constexpr
Date: Fri, 26 Feb 2021 12:29:15 +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: nickgray0 at brown dot edu
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-99287-4@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: Fri, 26 Feb 2021 12:29:16 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99287

            Bug ID: 99287
           Summary: std::source_location::function_name breaks constexpr
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nickgray0 at brown dot edu
  Target Milestone: ---

the following code seems to break constexpr-ness for std::string_view::find

    #include <source_location>
    #include <string_view>

    template<typename>
    consteval auto f() {
        return std::string_view{
std::source_location::current().function_name() };
    }

    auto main()->int {
        constexpr auto s =3D f<int>();
        constexpr auto x =3D s.find("int");
    }



error message: In file included from
/opt/compiler-explorer/gcc-trunk-20210226/include/c++/11.0.1/string_view:78=
1,
                 from <source>:2:
/opt/compiler-explorer/gcc-trunk-20210226/include/c++/11.0.1/bits/string_vi=
ew.tcc:
In function 'int main()':
<source>:11:30:   in 'constexpr' expansion of
's.std::basic_string_view<char>::find(((const char*)"int"), 0)'
/opt/compiler-explorer/gcc-trunk-20210226/include/c++/11.0.1/string_view:38=
4:26:
  in 'constexpr' expansion of '((const
std::basic_string_view<char>*)this)->std::basic_string_view<char>::find(__s=
tr,
__pos, std::char_traits<char>::length(__str))'
/opt/compiler-explorer/gcc-trunk-20210226/include/c++/11.0.1/bits/string_vi=
ew.tcc:62:20:
error: '(((std::basic_string_view<char>::size_type)((&"consteval auto f() [=
with
<template-parameter-1-1> =3D int]"[56]) - ((&"consteval auto f() [with
<template-parameter-1-1> =3D int]"[21]) + 1))) > 2)' is not a constant expr=
ession
   62 |       while (__len >=3D __n)
      |              ~~~~~~^~~~~~



Replacing std::source_location with the legacy
std::experimental::source_location seems to fix the problem.=