FreeTDS Development Group

[Chris <ccortner AT cvol.net>]

Hello Again :) I followed your directions here to get a backtrace. I
made sure that all the libraries involved were not stripped even httpd
and all its dependent libraries. PHP, FreeTDS and Apache are all
compiled with the -g flag. When I do a backtrace I get this, which Im
pretty sure is not going to be useful for you; no function names.  

Program received signal SIGSEGV, Segmentation fault.
0x402076fb in ?? ()
(gdb) bt 9
#0  0x402076fb in ?? ()
#1  0x40213df7 in ?? ()
#2  0x4020fa7c in ?? ()
#3  0x402152d7 in ?? ()
#4  0x401f0a04 in ?? ()
#5  0x402255a2 in ?? ()
#6  0x40225f65 in ?? ()
#7  0x402260fa in ?? ()
#8  0x400446f0 in __ieee754_scalbf () from /lib/i686/libm.so.6
(More stack frames follow...)
(gdb)

Am I missing something? Someone in a c programming channel on IRC
suggested I may have stack corruption. If this is what you want I'll
send the entire script file. I apologize in advance if this whole
segfault thing ends up being my fault. But I've checked and double
checked my environment and don't see what I could be missing.

Also in another post freddy 77 wrote:

> Two thing. This problem can be due to increase of numeric precision in
> libtds. You should recompile PHP (or PHP module) and retry.

I did do this again.. no luck.

Thanks
Chris - ccortner AT cvol.net

On Thu, 2002-11-14 at 22:28, James K. Lowden wrote:
> On 14 Nov 2002 16:18:55 -0600, Chris <ccortner AT cvol.net> wrote:
> > I only have a little bit of experience with gdb none with using it to
> > debug libraries. If you tell me what I need to do I'll do it, if
> > anything for the educational value. Otherwise I'm going home for the
> > night and I'll have to send you a backtrace sometime tommorow.
> 
> Hey, tomorrow's another day, right?  Didn't Scarlett say so?  
> 
> I hope I don't lead you on a wild goose chase; it's just that I can't
> think of a more definitive answer than a bt.  I really should write this
> up in the docs, because you're not the first fellow needing guidance.  I
> have to warn you, though, I'm not an Apache or PHP guy.  I write C++ and
> SQL for a living.  That means I can't really give you detailed
> instructions.  
> 
> The good news is that if we determine it's not a FreeTDS problem (which I
> fear it may be), you won't have to repeat this effort.  You can send the
> same bt to the PHP boys.  
> 
> First I should refer you to 
>       http://www.freetds.org/userguide/x2099.htm
> 
> which contains the earlier cautionary note that there is normally some
> environmental difference.  I'll remind others following along that the
> assertion here is that the environments are in fact identical, but that
> the script runs fine from the command line and bombs under apache.  
> 
> Before starting with gdb, you should make sure the symbols haven't been
> stripped (cf. strip(1)) from the executable.  Otherwise, we'll be looking
> at a machine eye view of the code, and, well, I won't be able to help you.
>  Use ldd(1) to check the executable's linkage, and file(1) to make sure it
> and the relevant libraries are not stripped.  For instance:
> 
> $ file *syb*so*
> libsybdb.so.1.0: NetBSD/i386 demand paged shared library not stripped
> libsybdb.so.2.0: NetBSD/i386 demand paged shared library not stripped
> 
> If the segfault left a .core file around and the executable isn't
> stripped, it might be possible to do a bt on it (gdb --core=httpd.core). 
> I haven't had much luck with that; I think it's because it doesn't work
> with shared libraries.  Maybe a real expert could explain why.  
> 
> What we want to do is start apache within gdb, and we don't want it to go
> into daemon mode or spawn children.  My apache docs say that's the -X
> switch.  
> 
> I think easiest is to make yourself a little .gdbinit file containing
> macros for gdb to execute when it starts.  That file would be in the
> current directory (wherever you launch gdb from) and would have:
> 
>       set args -X
>       directory /path/to/PHP/stuff
>       directory /path/to/FreeTDS/stuff
> 
> Then:
> 
> $ script bt
> $ gdb httpd
> (gdb) run
> [go to your test script and execute it against this server]
> segfault yada yada.....
> (gdb) bt 9
> [nine levels of unwraithlike call stack information]
> (gdb) quit
> $ ^D # closes script file "bt"
> 
> and send us the file that script(1) logged for you.  
> 
> Or something along those lines.  
> 
> > Thanks for all the help so far.
> 
> Surely.  Thanks for your patience.  One way or another, one of us will
> learn something.  
> 
> --jkl
> 
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