On Sat, 2 Mar 2019 at 17:15, David Brown <david@xxxxxxxxxxxxxxx> wrote: > > > > On 02/03/2019 14:46, Jonathan Wakely wrote: > > On Sat, 2 Mar 2019 at 13:42, Jonny Grant wrote: > >>>> Perhaps just adding to -Wextra would make sense? > >>> > >>> I would still be strongly against that. Why can't you just use > >>> -Wundef, instead of forcing everybody else to change their code to > >>> follow your preferred convention? > >> > >> Yes, we use it. Presumably someone decided what should go into -Wextra, > >> and presumably it is things that are worth adding... in my view it's > >> worth adding. No worries if that isn't consensus though! :) > > > > -Wundef is only useful if your code always does: > > > > #if defined(MACRO) && MACRO > > > > instead of just #if MACRO. > > > > They are both perfectly valid ways to write your code. People who are > > happy to write the latter should not have to deal with warnings that > > are only useful to people who write the former. > > > > Actually, I think the way to use -Wundef is to write your code: > > #define enable_feature_X 1 > #define enable_feature_Y 0 > > #if enable_feature_X > ... > #endif > > #if enable_feature_Y > ... > #endif > > > I use -Wundef in my own code, and only ever make use of "defined" or > "#ifdef" if it is a predefined macro, something from third-party code, > or a define I expect to get from the command line. To me, it is vital > to write: > > #define enable_feature_Y 0 > > to show that this is an option that is available, but I am specifically > choosing not to use it. > > -Wundef helps enforce this and avoids mystical options that come from > nowhere or having things that /could/ be usefully enabled if only the > user knew about them. Yes, that's how glibc does it too.
