Re: Strange things in math.h under Intel OSX

Sounds like a bug. You should report it as such at <http://bugreporter.apple.com 
 >

Shantonu

On May 19, 2006, at 4:06 AM, Max Persson wrote:

> Hi there,
>
> It seems like Apple may have done some mistakes in their port
> of the standard c library (which I seriously doubt). I bumped in to
> this problem when I compiled
> some tests for OpenEXR (under Intel OS X on a MacBook Pro). It says
> that a function from math.h is invalid. As you may know, there are two
> versions of some of the stuff in the std-c library, one for ppc and
> the other for i386. math.h is one of them. There is a macro/function
> called isnan() that determines if a float is a number or not, and it
> was here I bumped into the strange things. I opened up both versions
> of math.h and compared the implementation of the isnan() macro...
>
>
> Here is the one in the i386 math.h:
>
> #define isnan(x)        \
>       (       sizeof (x) == sizeof(float )    ?       __isnanf 
> (x)     \
>       :       sizeof (x) == sizeof(double)    ?       __isnand 
> (x)     \
>
>        :       __isnan (x))
>
>
> And here is the one from the ppc math.h:
>
> #define      isnan( x )         ( ( sizeof ( (x) ) == sizeof(double) )
> ?           \
>                             __isnand ( (double)(x) ) :
>                 \
>                               ( sizeof ( (x) ) == sizeof( float) ) ?
>          \
>                             __isnanf ( (float)(x) ) :
>                \
>                             __isnan  ( ( long double )(x) ) )
>
>
> The one that is used in my particular case is the first of them as I
> am on a i386 OS X. What I have learnt, you always put surrounding
> parenthesis in macros to prevent them from failing due to strange
> input. That is NOT the case in the i386 math.h (along with a couple of
> other macros there too).
>
>
> The input argument in the call to the isnan() macro is in this case:
>
> isnan(pf[y][x])
>
>
> What I belive is happening here is that the macro gets very confused
> with the array access here, because of the missing input parenthesis
> in the macro. This is what I got from the compiler to further
> strengthen the theory:
>
> testTiledCompression.cpp:59: error: expected unqualified-id before  
> 'sizeof'
> testTiledCompression.cpp:59: error: expected `)' before 'sizeof'
>
>
> But enough talking about this. I do not look for a quick fix here,
> what I'm concerned about is that Apple may have delivered a faulty
> math.h file for the Intel version of OS X. What do you think about it?
>
>
> Kind regards,
> Max Persson
>
> MFX AB, Sweden
> www.mfx.se
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