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 BE727385783A; Wed, 14 Oct 2020 10:08:35 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org BE727385783A
From: "chfast at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/97415] New: Invalid pointer comparison in
 stringbuf::str() (reported by pointer-compare AddressSanitizer)
Date: Wed, 14 Oct 2020 10:08:35 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 10.2.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: chfast 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-97415-4@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: Wed, 14 Oct 2020 10:08:35 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97415

            Bug ID: 97415
           Summary: Invalid pointer comparison in stringbuf::str()
                    (reported by pointer-compare AddressSanitizer)
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chfast at gmail dot com
  Target Milestone: ---

When my application is instrumented with -fsanitize=3Daddress,pointer-compa=
re
and running under ASAN_OPTIONS=3Ddetect_invalid_pointer_pairs=3D2,
I get for following failure in basic_stringbuf::str()

=3D=3D3879=3D=3DERROR: AddressSanitizer: invalid-pointer-pair: 0x7ffcdf273b=
66
0x000000000000
    #0 0x5597a6c6d786 in std::__cxx11::basic_stringbuf<char,
std::char_traits<char>, std::allocator<char> >::str() const
/usr/include/c++/10/sstream:184
    #1 0x5597a6c6d786 in std::__cxx11::basic_ostringstream<char,
std::char_traits<char>, std::allocator<char> >::str() const
/usr/include/c++/10/sstream:678
    #2 0x5597a6c6d786 in std::basic_ostream<char, std::char_traits<char> >&
std::__detail::operator<< <char, std::char_traits<char>,
std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<cha=
r> >
const&>(std::basic_ostream<char, std::char_traits<char> >&,
std::__detail::_Quoted_string<std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > const&, char> const&)
/usr/include/c++/10/bits/quoted_string.h:130
    #3 0x5597a6c6d786 in std::basic_ostream<char, std::char_traits<char> >&
std::filesystem::__cxx11::operator<< <char, std::char_traits<char>
>(std::basic_ostream<char, std::char_traits<char> >&,
std::filesystem::__cxx11::path const&) /usr/include/c++/10/bits/fs_path.h:4=
41
    #4 0x5597a6c6d786 in log_total
/home/builder/project/test/spectests/spectests.cpp:675
    #5 0x5597a6c48939 in run_tests_from_dir
/home/builder/project/test/spectests/spectests.cpp:708
    #6 0x5597a6c48939 in main
/home/builder/project/test/spectests/spectests.cpp:750

Here is the implementation of basic_stringbuf::str() used for compilation:

      __string_type
      str() const
      {
        __string_type __ret(_M_string.get_allocator());
        if (this->pptr())
          {
            // The current egptr() may not be the actual string end.
            if (this->pptr() > this->egptr())
              __ret.assign(this->pbase(), this->pptr());
            else
              __ret.assign(this->pbase(), this->egptr());
          }
        else
          __ret =3D _M_string;
        return __ret;
      }

In the line `if (this->pptr() > this->egptr())`,
the `this->egptr()` may be nullptr and therefore AddressSanitizer complains
about this comparison.

I don't have handy repro code for the issue, but I can try to build one if
desired.

GCC version: cpp (Debian 10.2.0-15) 10.2.0=