Re: libstdc++/1857: bitset::operator<<= and >>= incorrect for multiples of 32

Re: libstdc++/1857: bitset::operator<<= and >>= incorrect for multiples of 32

[nathan]

Synopsis: bitset::operator<<= and >>= incorrect for multiples of 32

State-Changed-From-To: analyzed->closed
State-Changed-By: nathan
State-Changed-When: Fri Jun  8 11:34:55 2001
State-Changed-Why:
    Peter Schmid <schmid@snake.iap.physik.tu-darmstadt.de>
    reports it is fixed.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=1857&database=gcc

libstdc++/1857: bitset::operator<<= and >>= incorrect for multiples of 32

[anders]

>Number:         1857
>Category:       libstdc++
>Synopsis:       bitset::operator<<= and >>= incorrect for multiples of 32
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bkoz
>State:          analyzed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Feb 03 09:26:07 PST 2001
>Closed-Date:    
>Last-Modified:  Wed Mar 22 11:17:00 PST 2000
>Originator:     Anders Johnson
>Release:        libstdc++-2.90.7
>Organization:
>Environment:
SunOS thresher 5.6 Generic_105181-05 sun4u sparc SUMW,Ultra-60
>Description:
The implementation of bitset relies on the behavior
of _WordT >> __BITS_PER_WORDT(_WordT), which is not
defined according to the C standard, and is equivalent
to _WordT >> 0 on the Sparc. This occurs whenever the
shift amount is a multiple of __BITS_PER_WORDT(_WordT).
>How-To-Repeat:

>Fix:
The expressions on lines 201 and 220 of stl/bits/std_bitset.h
should read (__offset ? ... : static_cast<_WordT>(0)) instead.
>Release-Note:

>Audit-Trail:

Formerly PR libstdc++/40


From: Benjamin Kosnik <bkoz@cygnus.com>
To: anders@ieee.org
Cc: libstdc++-gnats@sourceware.cygnus.com, libstdc++-prs@sourceware.cygnus.com
Subject: Re: libstdc++/40: bitset::operator<<= and >>= incorrect for multiples
 of 32
Date: Fri, 10 Mar 2000 11:17:48 -0800 (PST)

 can you please send me a patch and change log entry?
 
 thanks,
 benjamin
 
 
 On 10 Mar 2000 anders@ieee.org wrote:
 
 > 
 > >Number:         40
 > >Category:       libstdc++
 > >Synopsis:       bitset::operator<<= and >>= incorrect for multiples of 32
 > >Confidential:   no
 > >Severity:       serious
 > >Priority:       medium
 > >Responsible:    unassigned
 > >State:          open
 > >Class:          sw-bug
 > >Submitter-Id:   net
 > >Arrival-Date:   Thu Mar 09 20:57:00 PST 2000
 > >Closed-Date:
 > >Last-Modified:
 > >Originator:     Anders Johnson
 > >Release:        libstdc++-2.90.7
 > >Organization:
 > >Environment:
 > SunOS thresher 5.6 Generic_105181-05 sun4u sparc SUMW,Ultra-60
 > >Description:
 > The implementation of bitset relies on the behavior
 > of _WordT >> __BITS_PER_WORDT(_WordT), which is not
 > defined according to the C standard, and is equivalent
 > to _WordT >> 0 on the Sparc. This occurs whenever the
 > shift amount is a multiple of __BITS_PER_WORDT(_WordT).
 > >How-To-Repeat:
 > 
 > >Fix:
 > The expressions on lines 201 and 220 of stl/bits/std_bitset.h
 > should read (__offset ? ... : static_cast<_WordT>(0)) instead.
 > >Release-Note:
 > >Audit-Trail:
 > >Unformatted:
 > 
 
Responsible-Changed-From-To: unassigned->bkoz
Responsible-Changed-By: bkoz
Responsible-Changed-When: Wed Mar 22 00:30:10 2000
Responsible-Changed-Why:
    mine
State-Changed-From-To: open->analyzed
State-Changed-By: bkoz
State-Changed-When: Wed Mar 22 00:30:10 2000
State-Changed-Why:
    Can you please send in a patch for this?

From: bkoz@cygnus.com
To: anders@ieee.org, bkoz@cygnus.com, libstdc++-gnats@sourceware.cygnus.com,
  nobody@sourceware.cygnus.com
Cc:  
Subject: Re: libstdc++/40
Date: 22 Mar 2000 08:30:10 -0000

 Synopsis: bitset::operator<<= and >>= incorrect for multiples of 32
 
 Responsible-Changed-From-To: unassigned->bkoz
 Responsible-Changed-By: bkoz
 Responsible-Changed-When: Wed Mar 22 00:30:10 2000
 Responsible-Changed-Why:
     mine
 State-Changed-From-To: open->analyzed
 State-Changed-By: bkoz
 State-Changed-When: Wed Mar 22 00:30:10 2000
 State-Changed-Why:
     Can you please send in a patch for this?
 
 http://sourceware.cygnus.com/cgi-bin/gnatsweb.pl?cmd=view&pr=40&database=libstdc++

From: Benjamin Kosnik <bkoz@cygnus.com>
To: Anders Johnson <anders@broadcom.com>
Cc: libstdc++-gnats@sourceware.cygnus.com
Subject: Re: libstdc++/40
Date: Wed, 22 Mar 2000 11:05:11 -0800 (PST)

 No, I did not get your patch. Can you please resend, and cc 
 libstdc++-gnats? That way it gets logged in the database.
 
 thanks,
 benjamin

From: anders@broadcom.com (Anders Johnson)
To: bkoz@cygnus.com
Cc: libstdc++-gnats@sourceware.cygnus.com
Subject: Re: libstdc++/40
Date: Wed, 22 Mar 2000 11:13:14 -0800

 ----- Begin Included Message -----
 
 From anders Fri Mar 10 16:23:54 2000
 To: bkoz@cygnus.com
 Subject: Re: libstdc++/40: bitset::operator<<= and >>= incorrect for multiples
  of 32
 
 > can you please send me a patch and change log entry?
 
 I'm new at this, so please bear with me.
 
 The problem was actually observed on gcc/2.95.2/5.6/include/g++-3, because
 I can't build libstdc++-2.90.7 on my system because "wmemcmp.c" doesn't
 compile because 'wint_t' is not defined in either "string.h" or "stddef.h".
 However, the code in libstdc++-2.90.7 looks the same.
 
 Here is the patch:
 
 ----- Begin Included File -----
 
 diff -c3pr libstdc++-2.90.7-1/stl/bits/std_bitset.h libstdc++-2.90.7/stl/bits/std_bitset.h
 *** libstdc++-2.90.7/stl/bits/std_bitset.h	Tue Dec 21 21:07:58 1999
 --- NEW/stl/bits/std_bitset.h	Fri Mar 10 14:50:36 2000
 *************** void _Base_bitset<_Nw, _WordT>::_M_do_le
 *** 196,204 ****
       const size_t __offset = __shift % __BITS_PER_WORDT(_WordT);
       const size_t __sub_offset = __BITS_PER_WORDT(_WordT) - __offset;
       size_t __n = _Nw - 1;
 !     for ( ; __n > __wshift; --__n)
 !       _M_w[__n] = (_M_w[__n - __wshift] << __offset) |
 !                 (_M_w[__n - __wshift - 1] >> __sub_offset);
       if (__n == __wshift)
         _M_w[__n] = _M_w[0] << __offset;
       for (size_t __n1 = 0; __n1 < __n; ++__n1)
 --- 196,206 ----
       const size_t __offset = __shift % __BITS_PER_WORDT(_WordT);
       const size_t __sub_offset = __BITS_PER_WORDT(_WordT) - __offset;
       size_t __n = _Nw - 1;
 !     for ( ; __n > __wshift; --__n) {
 !       _M_w[__n] = (_M_w[__n - __wshift] << __offset);
 !       if(__offset)
 !         _M_w[__n] |= _M_w[__n - __wshift - 1] >> __sub_offset;
 !     }
       if (__n == __wshift)
         _M_w[__n] = _M_w[0] << __offset;
       for (size_t __n1 = 0; __n1 < __n; ++__n1)
 *************** void _Base_bitset<_Nw, _WordT>::_M_do_ri
 *** 215,223 ****
       const size_t __sub_offset = __BITS_PER_WORDT(_WordT) - __offset;
       const size_t __limit = _Nw - __wshift - 1;
       size_t __n = 0;
 !     for ( ; __n < __limit; ++__n)
 !       _M_w[__n] = (_M_w[__n + __wshift] >> __offset) |
 !                   (_M_w[__n + __wshift + 1] << __sub_offset);
       _M_w[__limit] = _M_w[_Nw-1] >> __offset;
       for (size_t __n1 = __limit + 1; __n1 < _Nw; ++__n1)
         _M_w[__n1] = static_cast<_WordT>(0);
 --- 217,227 ----
       const size_t __sub_offset = __BITS_PER_WORDT(_WordT) - __offset;
       const size_t __limit = _Nw - __wshift - 1;
       size_t __n = 0;
 !     for ( ; __n < __limit; ++__n) {
 !       _M_w[__n] = (_M_w[__n + __wshift] >> __offset);
 !       if(__offset)
 !         _M_w[__n] |= _M_w[__n + __wshift + 1] << __sub_offset;
 !     }
       _M_w[__limit] = _M_w[_Nw-1] >> __offset;
       for (size_t __n1 = __limit + 1; __n1 < _Nw; ++__n1)
         _M_w[__n1] = static_cast<_WordT>(0);
 
 ----- End Included File -----
 
 Here is a ChangeLog entry (not sure about the format):
 
 ----- Begin Included File -----
 
 - Fri Mar 10 16:12:00 PST 2000 stl/bits/std_bitset.h: Modified
 _M_do_left_shift and _M_do_right_shift not to rely on the behavior
 of _WordT << __BITS_PER_WORDT(_WordT), which is undefined according
 to the C standard, and does the wrong thing on Sparc.
 
 ----- End Included File -----
 
 Here is a test case:
 
 ----- Begin Included File -----
 
 #include <climits>
 #include <algobase.h>
 #include <bitset>
 #include <iostream>
 
 int main() {
 	bitset<66> b(1);
 	cout << b << endl;
 	b<<=32;
 	cout << b << endl;
 	b |= bitset<66>(1)<<65;
 	cout << b << endl;
 	b>>=32;
 	cout << b << endl;
 	return 0;
 }
 
 ----- End Included File -----
 
 The expected output is:
 000000000000000000000000000000000000000000000000000000000000000001
 000000000000000000000000000000000100000000000000000000000000000000
 100000000000000000000000000000000100000000000000000000000000000000
 000000000000000000000000000000001000000000000000000000000000000001
 
 The actual output on SunOS 5.5.1 sun4u sparc is:
 000000000000000000000000000000000000000000000000000000000000000001
 010000000000000000000000000000000100000000000000000000000000000000
 110000000000000000000000000000000100000000000000000000000000000000
 000000000000000000000000000000001100000000000000000000000000000011
 
 Please let me know if you need anything else.
 
 Thanks,
 --
  n  _   _ _    Anders Johnson        ``The ultimate test of all
  X /_)|' (_`   Broadcom Corporation    knowledge is experiment.''
 (_X\_,|  ._)   anders(at)ieee(dot)org         -- Richard Feynman
 
 
 
 ----- End Included Message -----
 
>Unformatted: