Re: Old dblib.c bug still there

On Tue, Jun 14, 2016 at 7:43 AM, Thompson, William <[email protected]
> wrote:

> I Agree with Freddy - if you want to make a change to test it out, I'd
> make the change to defncopy.c
> Try changing that NTBSTRINGBIND to plain old STRINGBIND, and see how that
> affects the behaviour.
> It looks to me like it should stop the trailing blanks from being stripped
> off
>
>
>
Gave this a shot.  In my test stored procedure, it now adds around 12,000
extra spaces. Not quite what I was hoping for.  :)  Looks like it wants to
pad it out to 16,000 chars.

I think it would work correctly if limited_dest_space weren't set in
dblib.c copy_data_to_host_var().

Yes, I changed line 577 of defncopy.c from:

erc = dbbind(dbproc, ctext, NTBSTRINGBIND, sizeof(sql_text), (BYTE *)
sql_text);

to:

erc = dbbind(dbproc, ctext, STRINGBIND, 0, (BYTE *) sql_text);


And now defncopy is working correctly on my test stored procedure.  Is this
going to mess anything else up, though?




>
> -----Original Message-----
> From: FreeTDS [mailto:[email protected]] On Behalf Of
> Frediano Ziglio
> Sent: 14 June 2016 12:58
> To: FreeTDS Development Group
> Subject: Re: [freetds] Old dblib.c bug still there
>
> 2016-06-12 18:59 GMT+01:00 Nem W Schlecht <[email protected]>:
> > Hello all,
> >
> > First off, I just want to thank all of the developers in this
> > community for continuing work on such a useful and excellent
> > application.  I cannot thank and appreciate you all enough!  Thank you,
> Thank You, THANK YOU!!
> >
> >
> > I recently grabbed the last stable release and came across an issue
> > that seems to constantly be plaguing me and has been around for a long
> > time.  I had reported this back in July of 2014, but the proposed
> > solution (stripping all but one space) would still screw up some of my
> > stored procedures (that have lots of spaces in strings for formatting
> purposes).
> >
> > My original post and reply:
> >   http://lists.ibiblio.org/pipermail/freetds/2014q3/028964.html
> >   http://lists.ibiblio.org/pipermail/freetds/2014q3/028966.html
> >
> > The issue is with lines 7311-7314 in dblib.c:
> >
> >    7311                 case NTBSTRINGBIND: /* strip trailing blanks,
> null
> > term */
> >    7312                     while (srclen && src[srclen - 1] == ' ') {
> >    7313                         --srclen;
> >    7314                     }
> >
> > Looks like something good to do, right?  Get rid of any blanks that we
> > don't need.  However, this keeps messing up my output when I use
> "defncopy"
> > to dump out some of my stored procedures.
> >
>
> Well... this is the expected behaviour of NTBSTRINGBIND. The problem is
> not in dblib.c but in defncopy that expects a different behaviour.
>
> > If it just so happens that you have a large stored procedure or large
> > string in that stored procedure *and* there are one or more spaces
> > exactly at a multiple of byte 4000, dblib.c will strip out the spaces,
> > causing either data corruption or an SQL syntax error in the stored
> procedure.
> >
> > I'm attaching an example to reproduce the issue.
> >
> > Load in 'dbo.big_proc-load.sql' and then immediately run 'defncopy' to
> > dump it back out.  Each digit should have 40 spaces between it, but on
> > line 96, it only contains 8 spaces.  dblib grabbed the first 4000
> > bytes, saw there there were spaces, and truncated it back to the last
> non-space character.
> >
> > I've actually had this happen (just by pure chance) in actual code as
> > well, where a line like this:
> >
> >      SELECT some_field_name AS some_field_alias
> >
> > has been turned into:
> >
> >      SELECT some_field_nameAS some_field_alias
> >
> > Thus causing an error the next time the stored procedure is run, since
> > the field name is now incorrect.
> >
> > I've modified my copy of dblib.c and commented out lines 7312-7314 (as
> > I did so 2 years ago and I've had to negative effects), but would like
> > to hear thoughts/opinions of the developers and would really like this
> > issue fixed.
> >
> > Again, thank you all so much for all of your hard work on FreeTDS!
> >
>
> Seems that all bindings with varlen != 0 (as you don't want an overflow
> too):
> - does blank padding;
> - are limited;
> - strip blanks.
> All stuff you don't want for your usage. The possible solution is to not
> use binding but dbdata and family.
>
> Frediano
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-- 
Nem W Schlecht <http://www.emptec.com/>
 "Perl did the magic.  I just waved the wand."