$ cat foo.c
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

int
main(int argc, char *argv[])
{
    int i = 0;
    int length = 0;

    /* Segfault occurs here */
    length = strlen(argv[0]);

    for(i=0; i<(length-1); i++) {
        argv[0][i] = 'a';
    }
    argv[0][length - 1] = '\0';
    exit(EXIT_SUCCESS);
}