hacking-the-art-of-exploitation

addressof.c
#include
int main() {
int int_var = 5;
int *int_ptr;
}
int_ptr = &int_var; // put the address of int_var into int_ptr
The program itself doesn’t actually output anything, but you can probably
guess what happens, even before debugging with GDB.
reader@hacking:~/booksrc $ gcc -g addressof.c
reader@hacking:~/booksrc $ gdb -q ./a.out
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
(gdb) list
1 #include
2
3 int main() {
4 int int_var = 5;
5 int *int_ptr;
6
7 int_ptr = &int_var; // Put the address of int_var into int_ptr.
8 }
(gdb) break 8
Breakpoint 1 at 0x8048361: file addressof.c, line 8.
(gdb) run
Starting program: /home/reader/booksrc/a.out
Breakpoint 1, main () at addressof.c:8
8 }
(gdb) print int_var
$1 = 5
(gdb) print &int_var
$2 = (int *) 0xbffff804
(gdb) print int_ptr
$3 = (int *) 0xbffff804
(gdb) print &int_ptr
$4 = (int **) 0xbffff800
(gdb)
As usual, a breakpoint is set and the program is executed in the
debugger. At this point the majority of the program has executed. The first
print command shows the value of int_var, and the second shows its address
using the address-of operator. The next two print commands show that
int_ptr contains the address of int_var, and they also show the address of
the int_ptr for good measure.
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