% cat t.c
#include <stdlib.h>
#include <string.h>

int myfunc() {
        char* flart=NULL;
        memcpy(flart, "BANANAS", 8);
        return 1;
}

int main()
{
        myfunc();

        return 0;
}

% gcc -g t.c -o t
% ulimit -c unlimited
% ./t
Segmentation fault (core dumped)
% ls -l core
-rw------- 1 matthew matthew 143360 2007-12-05 18:02 core
% gdb t core
GNU gdb 6.6-debian
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i486-linux-gnu"...
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".

warning: Can't read pathname for load map: Input/output error.
Reading symbols from /lib/tls/i686/cmov/libc.so.6...done.
Loaded symbols for /lib/tls/i686/cmov/libc.so.6
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Core was generated by `./t'.
Program terminated with signal 11, Segmentation fault.
#0  0x08048354 in myfunc () at t.c:6
6               memcpy(flart, "BANANAS", 8);
(gdb) bt
#0  0x08048354 in myfunc () at t.c:6
#1  0x0804837b in main () at t.c:12
(gdb) l
1       #include <stdlib.h>
2       #include <string.h>
3
4       int myfunc() {
5               char* flart=NULL;
6               memcpy(flart, "BANANAS", 8);
7               return 1;
8       }
9
10      int main()
(gdb) frame 1
#1  0x0804837b in main () at t.c:12
12              myfunc();
(gdb) l
7               return 1;
8       }
9
10      int main()
11      {
12              myfunc();
13
14              return 0;
15      }
16
(gdb) quit

ulimit -c unlimited

df -h .