FreeTDS Development Group

["Lowden, James K" <LowdenJK AT bernstein.com>]

Eric, 

On your say-so, I'll revert those lines to their 1.12 arrangement.  You
fixed the problem and Brian's pretty sure the 1.13 effect was mistaken.
I'll even reinstate your calling card for future reference.  

Brian, I'll be at a cvs-capable keyboard in about an hour.  Please consider
it done.  

--jkl


> -----Original Message-----
> From: Eric Deutsch [mailto:edeutsch AT systemsbiology.org]
> Sent: July 8, 2002 4:24 PM
> To: TDS Development Group
> Subject: [freetds] RE: Losing last character of TEXT fields
> 
> 
> 
> Hi all, since it looks like my name was hacked out, I better speak up!
> I just downloaded the latest from CVS, and I agree that this TEXT
> truncation is a revived problem that was fixed and now broken 
> again.  As
> of convert.c:1.12, we had:
> 
>            memcpy(dest, src, cplen);
> !          /* 2001-06-15 Deutsch changed [cplen-1] to [cplen] */
> !          dest[cplen] = '\0';
>            return strlen(dest);
> 
> but then as of 1.13 ("ODBC patch from Viktar Klimkovitch" by brianb)
> 
>            memcpy(dest, src, cplen);
> !          dest[cplen-1] = '\0';
>            return strlen(dest);
> 
> I'd left my calling card in the code with the hope that anyone who
> wanted it different could contact me.  I would like very much 
> to revert
> to my fix and investigate why it was changed back.  My platform (Linux
> x86 to SQL Server 2000 w/ DBD::Sybase on TDS 7.0) needs 
> version A of the
> code else the last character gets trunctated.  Who has a test 
> case that
> clearly needs option B (Viktar?)  Let's see if we can settle this.
> 
> Thanks!
> Eric
> 
> 
> > -----Original Message-----
> > From: Lowden, James K [mailto:LowdenJK AT bernstein.com]
> > Sent: Monday, July 08, 2002 12:23 PM
> > To: TDS Development Group
> > Subject: [freetds] RE: Losing last character of TEXT fields
> > 
> > > From: L J Bayuk [mailto:lbayuk AT mindspring.com]
> > > Sent: July 7, 2002 9:30 PM
> > >
> > > When I select from a TEXT field, the last character of
> > > the value is lost. (CHAR and VARCHAR are OK).  This only happens
> when
> > > using a recent FreeTDS "current" CVS snapshot, not when using
> > > FreeTDS-0.53.  It works fine in 0.53.
> > >
> > > I think the problem is an off-by-1 error here in
> > > src/tds/convert.c in the
> > > function tds_convert_text():
> > >          cplen = srclen > destlen ? destlen : srclen;
> > >          memcpy(dest, src, cplen);
> > > *        dest[cplen-1] = '\0';
> > >          return strlen(dest);
> > 
> > Brian, what do think about this and the proposed patch?  
> The story in
> cvs
> > is
> > an unhappy one.  I looked at a diff for src/tds/convert.c between
> version
> > 1.12 and 1.13; there's a little tug of war over whether and 
> when cplen
> > should be decremented.  We seem to be oscillating between truncating
> the
> > data and overflowing the buffer.  :/  My ten foot pole says not to
> touch
> > it.
> > 
> > 
> > --jkl
> > 
> > > I think that (*) line should be: dest[cplen] = '\0';
> > > (that's how it was at 0.53) but it seems to me this could
> > > overflow the dest
> > > buffer.  I browsed the CVS on SourceForge and found that this
> > > was changed
> > > in rev 1.13 of that file on May 25, 2002 by Victor K. but it
> > > isn't clear
> > > why. I would like to propose the patch below. It changes it back,
> and
> > > includes another change to prevent dest buffer overflow, and
> > > a third change
> > > in how to get the return value. These make sense to me, and
> > > seem to work,
> > > but I'm new with this so dissenting opinions would be welcome...
> > >
> > > *** convert.c.bak Tue Jun 25 21:44:27 2002
> > > --- convert.c     Sat Jul  6 10:41:43 2002
> > > ***************
> > > *** 122,131 ****
> > >      switch(desttype) {
> > >         case SYBTEXT:
> > >         case SYBCHAR:
> > > !          cplen = srclen > destlen ? destlen : srclen;
> > >            memcpy(dest, src, cplen);
> > > !          dest[cplen-1] = '\0';
> > > !          return strlen(dest);
> > >         case SYBBINARY:
> > >            cplen = srclen > destlen ? destlen : srclen;
> > >            memcpy(dest, src, cplen);
> > > --- 122,131 ----
> > >      switch(desttype) {
> > >         case SYBTEXT:
> > >         case SYBCHAR:
> > > !          cplen = srclen >= destlen ? destlen-1 : srclen;
> > >            memcpy(dest, src, cplen);
> > > !          dest[cplen] = '\0';
> > > !          return cplen;
> > >         case SYBBINARY:
> > >            cplen = srclen > destlen ? destlen : srclen;
> > >            memcpy(dest, src, cplen);
> > 
> > ---
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