Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
I have a trace() macro I turn on and off with another macro, e.g.
#ifdef TRACE
#define trace(x) trace_val(x, 0)
#else
#define trace(x) 0
#endif
This generates warning: statement with no effect from gcc when I call trace() with TRACE undefined. After a little searching I found that changing
#define trace(x) 0
to
#define trace(x) (void)0
silences the error. My question is: Why? What’s the difference?
The cast to void makes it clear that the programmer intends to throw the result away. The purpose of the warning is to indicate at that it’s not obvious that the statement has no effect and thus it’s useful to alert the programmer to that in case it was unintentional. A warning here would serve no purpose.