Here is an example that works for me. Environment: Debian Lenny amd64 8 GB RAM (probably doesn't matter) Linux 2.6.26-1-amd64 echo 0 >/proc/sys/kernel/randomize_va_space # important! linux-image-amd64 2.6.26+17 gcc 4:4.3.2-2 gdb 6.8-3 emacs 22.2+2-5
Code:
---------------------------------------
/* gcc -W -Wall -Wextra -O0 -g3 -o tt tt.c
*/
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
int *arr = 0;
if (argc)
{
arr = malloc(1000000 * sizeof(int));
arr[300000] = 17;
printf("arr[300000] = %d\n",arr[300000]);
argv = argv;
}
return 0;
}
---------------------------------------
Compile: gcc -W -Wall -Wextra -O0 -g3 -o tt tt.c
Debug (in Emacs): emacs &
M-x gdb
gdb --annotate=3 tt
b main
r # stops in main
b 16 # the printf line
c
p arr[300000] # gives $1 = 17
p &arr[300000] # gives $2 = (int *) 0x7ffff77e2f90 on my system
watch *(int *) 0x7ffff77e2f90
# gives Hardware watchpoint 3: *(int *) 140737345630096
c # gives Program exited normally
r # gives the following output
---------------------------------
Starting program: /home/cfischer/tmp/tt
Error in re-setting breakpoint 3: Cannot access memory at address 0x7ffff77e2f90
Error in re-setting breakpoint 3: Cannot access memory at address 0x7ffff77e2f90
Error in re-setting breakpoint 3: Cannot access memory at address 0x7ffff77e2f90
Cannot access memory at address 0x7ffff77e2f90
(gdb)
Debugger aborted
---------------------------------
--
Claus Fischer <claus.fisc...@clausfischer.com>
http://www.clausfischer.com/
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