 | | | Memory access problem with DBI or DBD-Mysql? | Memory access problem with DBI or DBD-Mysql? 2006-08-15 - By Federico Giannici
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Since there has been no reply to my previous message, I have done
further investigations trying to find the problem.
Please note that my knowledge of DBI/DBD is almost null, so the
followings are only simple suppositions.
I have seen that mysql_st_internal_execute() function is executed by
both the "do" and "execute" methods. It seems that the problems are only
with the "do" method and not with the "execute", so I looked for the
differences between them.
The main difference seems to be that "execute" passes a STATEMENT handle
as first argument, while "do" passes a DATABASE handle. The
mysql_st_internal_execute() function uses this handle to obtain the sth
and then from this one the dbh.
So, my hypothesis is that if the initial handle is a database one, the
sth (and the derived dbh) obtained from this is not a valid one!
Anybody can confirm (or negate) this wild hypothesis?
Thanks.
P.S.
I want to repeat that the problem manifest itself only under OpenBSD
because of it's memory management that cause the program to segfault if
try to access a non allocated memory. In other operating systems, a
random value is get for "imp_dbh->bind_type_guessing", which is almost
irrelevant.
Federico Giannici wrote:
> It seems to me that there is some kind of memory access problem with DBI
> or DBD-Mysql.
>
> I'm using OpenBSD 3.9-stable amd64. On OpenBSD 3.3 i386 the problem
> didn't appeared. As you may know, recent version of OpenBSD have a new
> kind of memory handling that make the programs segfault when they try to
> access no (longer) allocated memory.
>
> I'm using DBI 1.45 and DBD-Mysql 2.9008. I tried DBI 1.52 and DBD-Mysql
> 3.0006, but the problems were more frequent, so I remained to the old
> versions.
>
> Here is the problem: frequently some "do" commands cause perl to crash
> with signal 11. The crashes seems to depend on a lot of factors. For
> example, loading more libraries could make the program to start working.
> I think it depends on the structure of the memory allocated to the program.
>
> Here is the "bt" output of the core dump:
>
> #0 0x000000005260a736 in mysql_st_internal_execute (h=0x4713b6e0,
> statement=0x479b7140, attribs=0x4aa5fd40, numParams=0, params=0x0,
> cdaPtr=0x7f7ffffc8610, svsock=0x43c90498, use_mysql_use_result=0) at
> dbdimp.c:1654
> #1 0x0000000052612da3 in XS_DBD__mysql__db_do (cv=0x40970b20) at
> mysql.xs:222
> #2 0x0000000050ddf07b in XS_DBI_dispatch () from
> /usr/local/libdata/perl5/site_perl/amd64-openbsd/auto/DBI/DBI.so
> #3 0x000000004a5a1c47 in Perl_pp_entersub () at
> /usr/src/gnu/usr.bin/perl/pp_hot.c:2890
> #4 0x000000004a60899e in Perl_runops_standard () at
> /usr/src/gnu/usr.bin/perl/run.c:37
> #5 0x000000004a5f744d in S_run_body (oldscope=1) at
> /usr/src/gnu/usr.bin/perl/perl.c:1936
> #6 0x000000004a5f7231 in perl_run (my_perl=0x45356258) at
> /usr/src/gnu/usr.bin/perl/perl.c:1855
> #7 0x0000000000401afe in main ()
>
> I have found the problem is caused by accessing
> "imp_dbh->bind_type_guessing" for the call to ParseParam() inside
> mysql_st_internal_execute().
>
> I have verified that "imp_dbh" is NOT null, but trying to access any
> member make the program segfault. So maybe the pointer is a stale one?
>
> I have not enough knowledge of DBI to make more debugging.
>
>
> Bye.
>
--
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__
|- giannici@(protected)
|ederico Giannici http://www.neomedia.it
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