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Sender: "Alastair D'Silva" <alastair@newmillennium.net.au>
To: <internals@lists.php.net>
Date: Sun, 13 Feb 2005 16:24:42 +1100
Organization: New Millennium Networking
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Subject: Symbol clash between Recode and MySQL extensions
From: php@newmillennium.net.au

On FreeBSD, I was gettting the following error message when PHP exits:

Php in free(): junk pointer, too high to make sense

Further investigation showed that it stops showing when the MySQL module =
is
disabled. I rebuilt my MySQL client libraries with debugging symbols, =
and
forced a crash on invalid frees. Here is a backtrace:

(gdb) bt
#0  0x283fb404 in kill () from /usr/lib/libc.so.4
#1  0x28440810 in abort () from /usr/lib/libc.so.4
#2  0x2843f18a in isatty () from /usr/lib/libc.so.4
#3  0x2843f1bf in isatty () from /usr/lib/libc.so.4
#4  0x28440208 in isatty () from /usr/lib/libc.so.4
#5  0x28440485 in free () from /usr/lib/libc.so.4
#6  0x28487962 in my_no_flags_free (ptr=3D0x28d365e8
"U\211=E5\203=EC\024S=E8=F0=FF=FF=FF\201=C3Xo\017") at my_malloc.c:60
#7  0x2848c7a6 in delete_dynamic (array=3D0x824b798) at array.c:236
#8  0x2848ddad in hash_free (hash=3D0x824b780) at hash.c:116
#9  0x28d38b74 in recode_delete_outer () from =
/usr/local/lib/librecode.so.3
#10 0x28ceed88 in zm_shutdown_recode () from
/usr/local/lib/php/20041030/recode.so
#11 0x81145be in module_destructor ()
#12 0x81170d7 in zend_hash_apply_deleter ()
#13 0x8117246 in zend_hash_graceful_reverse_destroy ()
#14 0x810faa2 in zend_shutdown ()
#15 0x80d8a10 in php_module_shutdown ()
#16 0x8157eea in main ()
#17 0x80632a1 in _start ()

It looks like the MySQL hash_free function is being called as the recode
extension shuts down. I confirmed this by disabling the recode module =
and
noting that the problem went away (it also goes away if the MySQL module =
is
disabled).

Any thoughts on how to scope the libraries to avoid this conflict? I was
thinking dlfunc could be used to only import the functions we want, but =
I
don't really have time to play with this myself.

--=20
Alastair D'Silva           mob: 0413 485 733
Networking Consultant      fax: 0413 181 661
New Millennium Networking  web: http://www.newmillennium.net.au