Re: Old dblib.c bug still there

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
  


-----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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