Programming in C

392 Chapter 18 Debugging Programs

fprintf (stderr, "return %i\n", val);

#endif

return val;

}

int main (int argc, char *argv[])

{

int arg1 = 0, arg2 = 0;

if (argc > 1)

arg1 = atoi (argv[1]);

if (argc == 3)

arg2 = atoi (argv[2]);

#ifdef DEBUG

fprintf (stderr, "processed %i arguments\n", argc - 1);

fprintf (stderr, "arg1 = %i, arg2 = %i\n", arg1, arg2);

#endif

printf ("%i\n", process (arg1, arg2));

return 0;

}

Program 18.2 Output

$ gcc –D DEBUG p18-2.c Compile with DEBUG defined

$ a.out 5 10

processed 2 arguments

arg1 = 5, arg2 = 10

process (5, 10)

return 50

50

Program 18.2 Output (Rerun)

$ gcc p18-2.c Compile without DEBUG defined

$ a.out 2 5

10

When the program is ready for distribution, the debugging statements can be left in the

source file without affecting the executable code, as long as DEBUGisn’t defined. If a bug

is found at some later time, the debugging code can be compiled in and the output

examined to see what’s happening.

The previous method is still rather clumsy because the programs themselves tend to

be difficult to read. One thing you can do is change the way the preprocessor is used.

Program 18.2 Continued