Re: CGFloat and 64 Bit
Re: CGFloat and 64 Bit
- Subject: Re: CGFloat and 64 Bit
- From: "Sean McBride" <email@hidden>
- Date: Mon, 9 Feb 2009 15:10:48 -0500
- Organization: Rogue Research Inc.
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 email@hidden
Rogue Research www.rogue-research.com
Mac Software Developer Montréal, Québec, Canada
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