Re: Bug in tracing in DBD::Oracle

On 27/01/10 15:52, Martin Evans wrote:
> Hi,
> 
> I was asked to enable ora_verbose and send a trace a few days ago.
> 
> I'm getting a segfault with DBD::Oracle when ora_verbose or dbd_verbose
> is set to 15 in the connect method call. The stack trace is:
> 
> (gdb) bt
> #0  0x080be45c in Perl_sv_vcatpvfn ()
> #1  0x080ccd6d in Perl_vnewSVpvf ()
> #2  0x0811cb54 in PerlIO_vprintf ()
> #3  0x0811cbdf in PerlIO_printf ()
> #4  0x007e961c in ora_db_login6 (dbh=0x830f6a0, imp_dbh=0x834b0b0,
> dbname=<value optimised out>, uid=0x81aedf8 "bet",
>     pwd=0x81aee08 "b3t", attr=0x830ee20) at dbdimp.c:546
> #5  0x007dd0e0 in XS_DBD__Oracle__db__login (my_perl=0x8188008,
> cv=0x8344b88) at ./Oracle.xsi:100
> #6  0x080b12c0 in Perl_pp_entersub ()
> #7  0x080af688 in Perl_runops_standard ()
> #8  0x080acf4b in Perl_call_sv ()
> #9  0x00575f0a in XS_DBI_dispatch (my_perl=0x8188008, cv=0x82bfa88) at
> DBI.xs:3442
> #10 0x080b12c0 in Perl_pp_entersub ()
> #11 0x080af688 in Perl_runops_standard ()
> #12 0x080adbb2 in perl_run ()
> #13 0x08063ffd in main ()
> 
> and that refers to the following line in dbdimp.c:
> 
> OCINlsEnvironmentVariableGet_log_stat( &ncharsetid,(size_t)  0,
> OCI_NLS_NCHARSET_ID, 0, &rsize ,status );
> 
> Oracle defines the second argument as size_t so I guess that cast of 0
> to size_t is ok but ocitrace.h then goes on to cast it again to
> (unsigned long long) and the format argument has been changed to %llu.
> Although these match it segfaults.

I am responsible for this change. It was part of a campaign to avoid warnings
when compiling on 64-bit gcc platforms. All that is necessary to avoid
the compiler warnings is that the format arguments match the casts
(subject to integral promotion).

I used (unsigned long long) in this case for maximum portability. I couldn't
find any standard that said that (size_t) might not be wider than
(unsigned long).

If my change breaks PerlIO_vprintf, we must back off. Using (unsigned long)
and %lu would work on all platforms I use. Using (unsigned int) and %u,
would work in this case, but not for all uses of size_t.

This is the only place where I used a %llu or %lld, so there is only
one place to change.

Martin, can you try changing the casts to (unsigned long) and the formats
to %lu, and see if this fixes your problem.

> This segfaults on my Linux machine described with the Perl -V output
> below. I cannot believe the size of the first argument passed to
> OCINlsEnvironmentVariableGet is every going to need a size_t and in any
> case it has a max size of OCI_NLS_MAXBUFSZ (100 in Instant Client 11.1
> for Linux X86).

-- 
Charles Jardine - Computing Service, University of Cambridge
[email protected]    Tel: +44 1223 334506, Fax: +44 1223 334679