stackoverflow-9767686-C

/***
 *  Compares two methods of testing bit 5
 *  Clarify compiler behaviour for stackoverflow.com topic 9767686
 *
 *  main.c
 *
 *  Created by G Bulmer on 19/03/2012.
 */

#include "dummy_printf.h"   // get rid of stdio.h
#include "original_bit5.h"
#include "my_bit5.h"

int main (int argc, const char * argv[]) {
    int number = 16;

    original_bit5(number);

    my_bit5(number);

    return 0;
}


/***
 *  original_bit5.c
 */
#include "dummy_printf.h"   // get rid of stdio.h
#include "original_bit5.h"

void original_bit5(int number) {
    int mask = 1<<5;

    if ((number & mask) == 0)
        dummy_printf("Bit is off");
    else
        dummy_printf("its on");
}


/***
 *  my_bit5.c
 */
#include "dummy_printf.h"   // get rid of stdio.h
#include "my_bit5.h"

void my_bit5(int number) {
    dummy_printf((number & 0x20)?"its on":"Bit is off");
}


/***
 *  dummy_printf.c
 */
#include "dummy_printf.h"

void dummy_printf(const char* str) {
    const volatile const char* port = (const char*)0x20000000;

    port = str;     // stop the compiler throwing anything away
}


/***
 *  dummy_printf.h
 */
#ifndef _DUMMY_PRINTF_H_
#define _DUMMY_PRINTF_H_

void dummy_printf(const char* str);

#endif


/***
 *  original_bit5.h
 */
#ifndef _ORIGINAL_BIT5_H_
#define _ORIGINAL_BIT5_H_

extern void original_bit5(int number);

#endif


/***
 *  my_bit5.h
 */
#ifndef _MY_BIT5_H_
#define _MY_BIT5_H_

extern void my_bit5(int number);

#endif