On Sat, Nov 02, 2024 at 10:36:10PM +0100, Roland Illig wrote: > 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? > > Is the "- 0" in the first expression really necessary? If so, for which > cases?
I was just discussing this idiom a few days ago, in the context of program checkers that warn when you do #if SYM when it isn't defined (which is legal and well defined, but also often a mistake) and one of the virtues of this idiom is that such checkers can recognize it and shut up. For that purpose it's better to keep the parentheses as well as the arithmetic. -- David A. Holland dholl...@netbsd.org
