Home/ Questions/Q 8244917
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-07T22:01:03+00:00

For debug logging, I have often seen and used something like #ifdef DEBUG #define

  • 0

For debug logging, I have often seen and used something like

#ifdef DEBUG
    #define DLOG(fmt, args...) printf("%s:%d "fmt,__FILE__,__LINE__,args)
#else
    #define DLOG(fmt, args...)
#endif

but in a number of places, I have seen the second #define replaced with

#define DLOG(fmt, args...) do {} while (0)

In particular, there’s this answer, and the comment on this other answer to the same question suggests that the problem would be in a situation like

if (condition)
    DLOG("foo");

though my quick test suggests that the resulting semicolon on the line by itself will serve as the no-op statement inside the conditional.

Is one or the other of nothing and do {} while (0) better? If so, why? Is there something else that’s even better?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    See C #define macro for debug printing for an explanation of why you want a different form of no-op. You want to have the compiler parse the debug printing code even when you aren’t using it so that errors do not creep in.

    • 0