from 《征服C指针》

debug.c

#include <stdio.h>
#include <stdarg.h>

/* #define DEBUG */

#ifdef DEBUG
#define DEBUG_WRITE(args) DebugWrite args
#else
#define DEBUG_WRITE(args)
#endif

void DebugWrite(char *fmt,...)
{
    va_list ap;
    va_start(ap,fmt);
    vfprintf(stderr,fmt,ap);
    va_end(ap);
}

int sum(int times)
{
    DEBUG_WRITE(("%d\n",times));
    return (times) ? times + sum(times - 1) : 0;
}

int main()
{
    printf("%d",sum(10));
    return 0;
}