On 2/9/09 11:24 AM, Clark Cox said: >> Apple's headers inconsistently use #if and #ifdef. > >Because #if and #ifdef will both give the proper result in this >instance (i.e. the GCC compiler either defines __LP64__ to true, or it >doesn't define it at all), they are interchangeable. > >> I recommend: >> >> #if defined (__LP64__) && __LP64__ > >FYI, there is no functional difference between: > >#if defined (SOMEMACRO) && SOMEMACRO > >and > >#if SOMEMACRO > >That is, the preprocessor treats any undefined identifier in an '#if' >or '#elif" as if it were defined to be zero.
I'm not a language lawyer, but I believe the latter is not guaranteed to evaluate to 0 if the macro is not defined. However, I imagine 99% of compilers will evaluate it to 0. gcc certainly does. This is the reason for the existance of -Wundef I believe. >> which will also not warn with -Wundef. > >My original #ifdef won't trigger this warning either True of course. >therefore it is >the best of all options (i.e. it's concise, doesn't trigger warnings, >and provides the correct result). True if __LP64__ is either defined to something or not defined at all. This is currently the case, but I could not find docs guaranteeing this. If it's ever defined to 0 then you'd have a problem. And seeing how Apple itself sometimes uses #if and sometimes #ifdef I think caution is advised. This is rather academic of course... :) -- ____________________________________________________________ Sean McBride, B. Eng s...@rogue-research.com Rogue Research www.rogue-research.com Mac Software Developer Montréal, Québec, Canada _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
