#include <stdio.h>

#include “reciprocal.hpp”

int main (int argc, char **argv)

{

int i;

i = atoi (argv[1]);

printf (“The reciprocal of %d is %g\n”, i, reciprocal (i));

return 0;

}

#include <cassert>

#include “reciprocal.hpp”

double reciprocal (int i) {

// I should be non-zero.

assert (i != 0);

return 1.0/i;

}

#ifdef __cplusplus

extern “C” {

#endif

extern double reciprocal (int i);

#ifdef __cplusplus

}

#endif

% gcc -c main.c

% g++ -c reciprocal.cpp

% g++ -c -I ../include reciprocal.cpp

#include "stdio.h"

#include "stdlib.h"

int main(int argc, char** argv){

int i = 3;

#ifdef CHANGEVALUE

i = 4;

#endif

printf("i = %d\n", i);

printf("PT = %f\n", PI);

}

% g++ -c -O2 reciprocal.cpp

% g++ -o reciprocal main.o reciprocal.o

% g++ -o reciprocal main.o reciprocal.o –lpam

% g++ -o reciprocal main.o reciprocal.o -L/usr/local/lib/pam –lpam

reciprocal: main.o reciprocal.o

g++ $(CFLAGS) -o reciprocal main.o reciprocal.o

main.o: main.c reciprocal.hpp

gcc $(CFLAGS) -c main.c

reciprocal.o: reciprocal.cpp reciprocal.hpp

g++ $(CFLAGS) -c reciprocal.cpp

clean:

rm -f *.o reciprocal

% make CFLAGS=-O2

gcc -O2 -c main.c

g++ -O2 -c reciprocal.cpp

g++ -O2 -o reciprocal main.o reciprocal.o

% make CFLAGS=-g

gcc -g -c main.c

g++ -g -c reciprocal.cpp

g++ -g -o reciprocal main.o reciprocal.o

% gdb reciprocal

(gdb) run

Starting program: reciprocal

(gdb) where

#0 __strtol_internal (nptr=0x0, endptr=0x0, base=10, group=0) at strtol.c:287

#1 0x40096fb6 in atoi (nptr=0x0) at ../stdlib/stdlib.h:251

#2 0x804863e in main (argc=1, argv=0xbffff5e4) at main.c:8

(gdb) up 2

#2 0x804863e in main (argc=1, argv=0xbffff5e4) at main.c:8

8 i = atoi (argv[1]);

(gdb) print argv[1]

$2 = 0x0

(gdb) break main

Breakpoint 1 at 0x804862e: file main.c, line 8.

(gdb) next

9 printf (“The reciprocal of %d is %g\n”, i, reciprocal (i));

(gdb) step

reciprocal (i=7) at reciprocal.cpp:6

6 assert (i != 0);