> In the system headers, we use this pattern a lot:
>> #if (_POSIX_C_SOURCE - 0 >= 200809L) || defined(_NETBSD_SOURCE)
> Are the parentheses around the first condition really necessary? If
> so, for which cases?
Probably not...I *think*.
> Is the "- 0" in the first expression really necessary? If so, for
> which cases?
The case where _POSIX_C_SOURCE is not defined at all. (Whether that
case is worth bothering with, that's arguable. But I think that's
probably the point of the -0.)
This is a valid #if:
#if ( - 0 > 200809L) || defined(_NETBSD_SOURCE)
This is not:
#if ( > 200809L) || defined(_NETBSD_SOURCE)
Of course, if _POSIX_C_SOURCE is defined as
do } case ~ ( ) j -
that won't help. But in that sort of case nothing will.
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