first class

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>

int a = 0;

void test() {
  a=0xabcd;
}

int main() {
  unsigned char Template[100];
  int Index = 0;

// make a copy of the test() function in Template and find where the constant is
  int i, Length;
  unsigned char *OldTemplate = (char*)test;
  for(i=0;i<50;i++) {
    Template[i] = OldTemplate[i];
    if((OldTemplate[i] == 0xcd) && (OldTemplate[i+1] == 0xab))
      Index = i;
    if(OldTemplate[i] == 0xc3) // x86 RET opcode
      break;
  }
  Length = i+1;

// display the function
  for(i=0;i<Length;i++) {
    if(i == Index || i == Index + 1)
      printf("xx ");
    else
      printf("%.2x ", Template[i]&255);
  }
  putchar('\n');

// create 20 functions that set a global variable 0 to 19
  char *Created[20];
  for(i=0;i<20;i++) {
    Created[i] = (void*)malloc(Length);
    memcpy(Created[i], Template, Length);
    Created[i][Index+0] = i;
    Created[i][Index+1] = 0;
  }

// call all the functions we just made
  for(i=0;i<20;i++) {
    void (*foo)(void) = (void*)Created[i];
    foo();
    printf("%i ", a);
  }
  putchar('\n');

}