hacking-the-art-of-exploitation

static.c
#include
void function() { // An example function, with its own context
int var = 5;
static int static_var = 5; // Static variable initialization
}
printf("\t[in function] var = %d\n", var);
printf("\t[in function] static_var = %d\n", static_var);
var++;
// Add one to var.
static_var++; // Add one to static_var.
int main() { // The main function, with its own context
int i;
static int static_var = 1337; // Another static, in a different context
}
for(i=0; i < 5; i++) { // Loop 5 times.
printf("[in main] static_var = %d\n", static_var);
function(); // Call the function.
}
The aptly named static_var is defined as a static variable in two places:
within the context of main() and within the context of function(). Since static
variables are local within a particular functional context, these variables can
have the same name, but they actually represent two different locations in
memory. The function simply prints the values of the two variables in its context
and then adds 1 to both of them. Compiling and executing this code will
show the difference between the static and nonstatic variables.
reader@hacking:~/booksrc $ gcc static.c
reader@hacking:~/booksrc $ ./a.out
[in main] static_var = 1337
[in function] var = 5
[in function] static_var = 5
[in main] static_var = 1337
[in function] var = 5
[in function] static_var = 6
[in main] static_var = 1337
[in function] var = 5
[in function] static_var = 7
[in main] static_var = 1337
[in function] var = 5
[in function] static_var = 8
[in main] static_var = 1337
[in function] var = 5
[in function] static_var = 9
reader@hacking:~/booksrc $
Programming 67