Hello,
Solaris 2.[89], perl 5.8.[35], net-snmp 5.1.2, 5.2.1.2 etc.
when using async bulkwalk I get bus error in do_clean_named_objs. I've
been chasing this bug for some hours. The problems seems to be that in
__push_cb_args called from _bulkwalk_finish the macro PUSHMARK(sp)
writes the number 3 into an xgv_gp referring to a sub in Exporter.pm.
do_clean_named_objs does not like that at all on exit and core dumps.
do_clean_named_objs get bus error while studying a SV at 0x3fa19c
poining to a sv_any at 0x1f2fd8 with a xgv_gp of value 3.
(gdb) p sv
$207 = (SV *) 0x3fa19c
(gdb) p *$
$208 = {sv_any = 0x1f2fd8, sv_refcnt = 1, sv_flags = 24589}
(gdb) p (((XPVGV*)(sv)->sv_any)->xgv_gp)
$209 = (GP *) 0x3
(gdb)
I do get that address repeatedly whenever I rerun the program so I when
Ilook at the address before the PUSHMARK(sp) erases the memory:
(gdb) p (((XPVGV*)0x1f2fd8)->xgv_gp)
$210 = (GP *) 0x402538
(gdb) p *(((XPVGV*)0x1f2fd8)->xgv_gp)
$211 = {gp_sv = 0x3fa154, gp_refcnt = 1, gp_io = 0x0, gp_form = 0x0, gp_av =
0x0, gp_hv = 0x0, gp_egv = 0x3fa19c, gp_cv = 0x3fa184, gp_cvgen = 0,
gp_flags = 0, gp_line = 65, gp_file = 0x217ec0
"/local/net/perl/5.8.5-debug/lib/5.8.5/Exporter.pm"}
It seems like that somehow PL_markstack_ptr overwrites an sub in
Exporter.pm. I try to find our how this happens:
Using gdb to breaking in _bulkwalk_finish and looking at
PL_markstack_ptr, the pointer starts out as 0x1f3034, and then
decreases 4 bytes every _bulkwalk_finish until it PL_markstack_ptr into
the area pointed by the sv_any:
PL_markstack_ptr starts at:
0x1f3030 start
0x1f3038 main_loop
0x1f3034 _bulkwalk_finish (decreases to 0x1f3030 at dXSARGS in
_bulkwalk_finish)
0x1f3030 _bulkwalk_finish (decreases to 0x1f302c at dXSARGS in
_bulkwalk_finish)
0x1f302c
...
..
decreases until
...
0x1f2ff8 _bulkwalk_finish (where the PUSHMARK(sp) in
__push_cb_args set the xgv_gp in the
(XPVGV*)0x1f2fd8 to 3.
I must say that I do not understand the dXSARGS, so using the
perlcall(1) manuall, I tried to change the dXSARGS to
dSP ;
ENTER ;
SAVETMPS;
...
FREETMPS ;
LEAVE ;
and then I get no more bus error and core dumps.
What is going on here? This is the first time for me looking at perl
internal, so I don't know really what is going on here. Does anybody
know how to fix this bus error?
Kind Regards,
Ole Bjørn Hessen.
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