Warning on floor and ceil on latest OS X devtools

[Asko Kauppi <askok@...>]

I was struck by this, it's still partly a mystery but hardly my  
imagination. :)

If you use Lua mathlib with -ffast-math, this shall effect you.

    Lua 5.1 (work4)  Copyright (C) 1994-2004 Tecgraf, PUC-Rio
    > print( math.floor(0.5) )
    0.5
    > print( math.ceil(0.7) )
    0.7

-ak


Edelleenlähetetty viesti alkaa:

> Lähettäjä: Asko Kauppi <asko.kauppi@sci.fi>
> Päiväys: 8. kesäkuuta 2005 11.32.02 GMT+03:00
> Vastaanottaja: fink-devel@lists.sourceforge.net
> Aihe: XCode 2.1 and -ffast-math
>
>
>
> Has anyone else experienced this weird bug, occurring after upgrade  
> to the new XCode 2.1:
>
> System:
>     OS X Tiger (10.4.1)
>     iMac G4 700MHz
>     XCode 2.1 (actually, using gcc from command line, but.. does it  
> matter)
>
> If -ffast-math is given to gcc, it #defines floor[f] and ceil[f] to  
> __fastmath_floor[f] and so.  These are inline functions that treat  
> -0.0 in a non-standard way. So what..
>
> For me, in some places, floorf(0.7)==0.7 !  That's no use.  Weird  
> thing is, that this is not consistent, some places work, others  
> don't.  Possibly some variable assignment/code generation/whatever  
> weirdness?
>
> Anyway, I did not have this (same code) before running XCode 2.1,  
> so clearly there's something wrong.
>
> If some of you would have XCode 2.0, please send /usr/include/ 
> architecture/ppc/math.h so I can compare them.  It may be the  
> function hasn't changed, but gcc code generation has, though.
>
> First aid:  just stop using '-ffast-math' or #undef the macros it  
> defines. Regular libm functions will be used, and they work. :)
>
> -ak