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 B43D33858C53; Tue, 13 Sep 2022 12:27:41 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org B43D33858C53
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1663072061;
	bh=EAQkWH8I5hfOmiTXVI48i3skNqriDwlOXoYmDXR/mGg=;
	h=From:To:Subject:Date:From;
	b=x6lrX0Rbxg6vAt7BIlYLO6URLe0z2RTN/OB77Rw+7UyQvMIuA243XG0VzZN3MSxz6
	 lQ9EzROGMsPGcsHSei+uzfOvrTz47WbF0Tu6KENu0c0EVWznrlADm8JorvaHzr6OAP
	 KVDPXNU6oncx+runn+7nYTAe6Yt3RUr1eFvXIlQU=
From: "jzwinck at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/106926] New: string_view construction from literal string
 containing null/zero should warn
Date: Tue, 13 Sep 2022 12:27:41 +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: 13.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jzwinck at gmail dot com
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-106926-4@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
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106926

            Bug ID: 106926
           Summary: string_view construction from literal string
                    containing null/zero should warn
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jzwinck at gmail dot com
  Target Milestone: ---

This code compiles but does something the programmer almost certainly does =
not
want:

    #include <string_view>
    constexpr std::string_view sv =3D "four\0nine"; // 9 bytes of data
    static_assert(sv.size() =3D=3D 4); // required by C++, but surprising

GCC can't implement what the programmer intended, so it should warn if a
string_view is constructed or assigned from a string literal which contains
null bytes before the end.

When this happens, the rest of the string literal data is still accessible =
but
only if you know it's there by some other means.  I expect such usage to be
very rare, so warning about it even at -Wall seems reasonable.  Even if the
warning only comes with -Wextra that would be better than silence.=