How to generate core dump file and debug with it?

1. Change core file size

[user@forever ~]$ ulimit -a

core file size          (blocks, -c) 0

data seg size           (kbytes, -d) unlimited

scheduling priority             (-e) 0

file size               (blocks, -f) unlimited

pending signals                 (-i) 8192

max locked memory       (kbytes, -l) 32

max memory size         (kbytes, -m) unlimited

open files                      (-n) 1024

pipe size            (512 bytes, -p) 8

POSIX message queues     (bytes, -q) 819200

real-time priority              (-r) 0

stack size              (kbytes, -s) 10240

cpu time               (seconds, -t) unlimited

max user processes              (-u) 8192

virtual memory          (kbytes, -v) unlimited

file locks                      (-x) unlimited

[user@forever ~]$ ulimit -c unlimited

[user@forever ~]$ ulimit -a

core file size          (blocks, -c) unlimited

data seg size           (kbytes, -d) unlimited

scheduling priority             (-e) 0

file size               (blocks, -f) unlimited

pending signals                 (-i) 8192

max locked memory       (kbytes, -l) 32

max memory size         (kbytes, -m) unlimited

open files                      (-n) 1024

pipe size            (512 bytes, -p) 8

POSIX message queues     (bytes, -q) 819200

real-time priority              (-r) 0

stack size              (kbytes, -s) 10240

cpu time               (seconds, -t) unlimited

max user processes              (-u) 8192

virtual memory          (kbytes, -v) unlimited

file locks                      (-x) unlimited

 

2. Generate core dump file

Example code:

  1 #include <iostream>

  2

  3 using namespace std;

  4

  5 int main(void)

  6 {

  7     char *ptr = (char*)malloc(1000);

  8

  9     free(ptr);

 10     free(ptr);

 11

 12     return 0;

 13 }

[user@forever cpp]$ g++ -g test2.cpp -o test2

[user@forever cpp]$ ./test2

*** glibc detected *** ./test2: double free or corruption (top): 0x095af008 ***

======= Backtrace: =========

/lib/libc.so.6[0x83e595]

/lib/libc.so.6(cfree+0x59)[0x83e9d9]

./test2(__gxx_personality_v0+0x198)[0x804862c]

/lib/libc.so.6(__libc_start_main+0xdc)[0x7eae9c]

./test2(__gxx_personality_v0+0x3d)[0x80484d1]

======= Memory map: ========

00732000-00733000 r-xp 00732000 00:00 0          [vdso]

0076f000-0077a000 r-xp 00000000 08:02 255748     /lib/libgcc_s-4.1.2-20080825.so.1

0077a000-0077b000 rwxp 0000a000 08:02 255748     /lib/libgcc_s-4.1.2-20080825.so.1

007b2000-007cc000 r-xp 00000000 08:02 256073     /lib/ld-2.5.so

007cc000-007cd000 r-xp 00019000 08:02 256073     /lib/ld-2.5.so

007cd000-007ce000 rwxp 0001a000 08:02 256073     /lib/ld-2.5.so

007d5000-00914000 r-xp 00000000 08:02 256637     /lib/libc-2.5.so

00914000-00916000 r-xp 0013f000 08:02 256637     /lib/libc-2.5.so

00916000-00917000 rwxp 00141000 08:02 256637     /lib/libc-2.5.so

00917000-0091a000 rwxp 00917000 00:00 0

00922000-00947000 r-xp 00000000 08:02 256638     /lib/libm-2.5.so

00947000-00948000 r-xp 00024000 08:02 256638     /lib/libm-2.5.so

00948000-00949000 rwxp 00025000 08:02 256638     /lib/libm-2.5.so

06f3c000-0701c000 r-xp 00000000 08:02 296348     /usr/lib/libstdc++.so.6.0.8

0701c000-07020000 r-xp 000df000 08:02 296348     /usr/lib/libstdc++.so.6.0.8

07020000-07021000 rwxp 000e3000 08:02 296348     /usr/lib/libstdc++.so.6.0.8

07021000-07027000 rwxp 07021000 00:00 0

08048000-08049000 r-xp 00000000 08:03 1436238    /home/user/cpp/test2

08049000-0804a000 rw-p 00000000 08:03 1436238    /home/user/cpp/test2

095af000-095d0000 rw-p 095af000 00:00 0          [heap]

b7f6e000-b7f70000 rw-p b7f6e000 00:00 0

bfad9000-bfaee000 rw-p bffea000 00:00 0          [stack]

Aborted (core dumped)

 

3. Debug core dump file

[user@forever cpp]$ gdb test2 core.6094

GNU gdb Fedora (6.8-37.el5)

Copyright (C) 2008 Free Software Foundation, Inc.

License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software: you are free to change and redistribute it.

There is NO WARRANTY, to the extent permitted by law.  Type "show copying"

and "show warranty" for details.

This GDB was configured as "i386-redhat-linux-gnu"...

 

warning: Can't read pathname for load map: Input/output error.

Reading symbols from /usr/lib/libstdc++.so.6...done.

Loaded symbols for /usr/lib/libstdc++.so.6

Reading symbols from /lib/libm.so.6...done.

Loaded symbols for /lib/libm.so.6

Reading symbols from /lib/libgcc_s.so.1...done.

Loaded symbols for /lib/libgcc_s.so.1

Reading symbols from /lib/libc.so.6...done.

Loaded symbols for /lib/libc.so.6

Reading symbols from /lib/ld-linux.so.2...done.

Loaded symbols for /lib/ld-linux.so.2

Core was generated by `./test2'.

Program terminated with signal 6, Aborted.

[New process 6094]

#0  0x00732402 in __kernel_vsyscall ()

(gdb) bt

#0  0x00732402 in __kernel_vsyscall ()

#1  0x007fddf0 in raise () from /lib/libc.so.6

#2  0x007ff701 in abort () from /lib/libc.so.6

#3  0x0083628b in __libc_message () from /lib/libc.so.6

#4  0x0083e595 in _int_free () from /lib/libc.so.6

#5  0x0083e9d9 in free () from /lib/libc.so.6

#6  0x0804862c in main () at test2.cpp:10

(gdb) q