It allows things like
if (condition)
test_errno(...);
to work properly with or without braces.
質問
What is the reason to define macro this way:
#define test_errno(msg) do{if (errno) {perror(msg); exit(EXIT_FAILURE);}} while(0)
I mean what is the reason behind do{}while(0)
? Of course it will be done once only, zero is constant, cannot change to nonzero somehow, so why to use such construction?
解決
It allows things like
if (condition)
test_errno(...);
to work properly with or without braces.
他のヒント
There is no good reason in this case. In similar constructs, it is useful for the statements inside to have continue
and break
to do useful things.
#define test_errno(msg) do {if (cond1) break; \
if (cond2) break; \
if (cond3) break; \
do_something_if_all_condtions_met();} while(0)