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Editorial Team
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Asked: 2026-06-03T04:19:19+00:00

I’m writing a logging class at the moment. The Logger works with streams and

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I’m writing a logging class at the moment. The Logger works with streams and also prints the object which is logging at the moment. Here is the macro:

#define OBJLOG(DL, what) DL <= this->Logger->getDebugLevel() ? *this->Logger << DL << "[" << this->Name << "]: "<< what << std::endl : this->Logger->doNothing();

The pseudo code Variant for better overview:

#define OBJLOG(debuglevel, what) debuglevel <= logger.debuglevel ? logger.log(what) : logger.doNothing()

Is there any way to get around the doNothing function call, like doing nothing at all?

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1 Answer

  1. Editorial Team
    #define OBJLOG(DL, what) do { if(DL <= this->Logger->getDebugLevel()) *this->Logger << DL << "[" << this->Name << "]: "<< what << std::endl; } while(0)

    See Why use apparently meaningless do-while and if-else statements in macros? for an explanation. (The do {} while(0) isn’t strictly necessary here, but I would prefer not to leak an ostream.)

    Also, you should always wrap macro argument uses in parentheses, like:

    #define OBJLOG(DL, what) do { if((DL) <= this->Logger->getDebugLevel()) *this->Logger << (DL) << "[" << this->Name << "]: "<< (what) << std::endl; } while(0)

    Finally, you should move this code into a function and call that in your macro (if you really insist on using a macro) to avoid evaluating your macro arguments more than once.

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