I see in some header files, such as Sun's <sys/feature_tests.h>, the value of a macro is subtracted by zero before testing it against a value. Example:
Why didn't they just writeCode:#if (_XOPEN_SOURCE - 0 == 600) || (_POSIX_C_SOURCE - 0 == 200112L) #define _XPG6 #undef _POSIX_C_SOURCE #define _POSIX_C_SOURCE 200112L #endif
#if (_XOPEN_SOURCE == 600) || (_POSIX_C_SOURCE == 200112L) ?
Should we follow their style?
because if _XOPEN_SOURCE is defined as empty string in their case you get
(-0 == 600) - valid expression
in your case
( == 600) - invalid expression
All problems in computer science can be solved by another level of indirection,
except for the problem of too many layers of indirection.
– David J. Wheeler
In that case, it would also achieve the same purpose if I write
#if (_XOPEN_SOURCE + 0 == 600)
, right?
I would have thought so.Originally Posted by hzmonte
--
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
