Date: Wed, 31 Jul 1996 18:42:53 +0200 (MET DST) From: Jean-Paul POIRET <jpp@vtcom.fr> To: FreeBSD questions <freebsd-questions@freebsd.org> Subject: Can really gdb examine a core file ? Message-ID: <Pine.BSF.3.91.960731182725.11439A-100000@deepthought.sv.vtcom.fr>
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Hello ! When I try a post-mortem analysis with Gdb of a C programm with a
bss array , like this es.c :
---------------------------
| int titi[1000]; |
| f() |
| { |
| int l = 4; |
| kill(getpid(),6); |
| } |
| main() |
| { |
| titi[0] = 461; |
| f(); |
| } |
---------------------------
gcc -g -c es.c
gcc -g -o es es.o
./es
Abort (core dumped)
Thus, I have got the core file:
-rw------- 1 jpp jpp 147456 Jul 31 18:34 es.core
Now, I wish to examine the core file :
gdb es es.core
GDB is free software and you are welcome to distribute copies of it
under certain conditions; type "show copying" to see the conditions.
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GDB 4.13 (i386-unknown-freebsd),
Copyright 1994 Free Software Foundation, Inc...
Core was generated by `es'.
Program terminated with signal 6, Abort trap.
#0 0x805fee5 in end ()
bt
(gdb) #0 0x805fee5 in end ()
Cannot access memory at address 0x309c.
(gdb)
It seems that the bt command can't retrieve the stack data.
-----------------------------------------------------------
Now, when I comment the two "titi" lines, the backtracking works again:
bt
(gdb) #0 0x805fee5 in end ()
#1 0x162c in f () at es.c:5
#2 0x1641 in main () at es.c:10
(gdb)
I tried gcore, some gcc options ... without result.
It seems that gdb on a core file gives always 0 for global data
---------------------------------------------------------------
contents too.
------------
However, without the two titi lines, we can read local data in the
core file (but not global data):
p f::l
(gdb) $1 = 4
(gdb)
Today, I run FreeBSD 2.1. I will switch to FreeBSD 2.1.5 in 2 weeks.
It could explain my problem, I suppose.
Does somebody meet with this gdb problem on core files too ?
Jean-Paul
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Jean-Paul POIRET Phone +33 1 46 12 67 90
VTCOM Solutions Vocales Fax +33 1 46 12 67 00
40, rue Gabriel Crie
92245 Malakoff FRANCE E-mail JeanPaul.Poiret@vtcom.fr
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