[CMake] Fwd: 64 bit flags

[pellegrini]

Thanks a lot Eric for the clear explanation.

Eric




Eric Noulard a écrit :
> I did forget the ML.
>
>
> ---------- Forwarded message ----------
> From: Eric Noulard <eric.noulard at gmail.com>
> Date: 2011/9/9
> Subject: Re: [CMake] 64 bit flags
> To: pellegrini <pellegrini at ill.fr>
>
>
> 2011/9/9 pellegrini <pellegrini at ill.fr>:
>   
>> Hello everybody,
>>
>> I have a Fortran project that is currently built (using gfortran, g95 or
>> ifort) on 32 bits machines but that might need quite soon to be built on 64
>> bit machines as well.
>>
>> Does cmake automatically detect the processor architecture and add the 64
>> bit flag at configuration time or do I have to declare those flags through,
>> for example, a '-D option ?
>>     
>
> CMake chose the default target architecture of your compiler so
> if the default target ofthe compiler is 64bits no need for special flags.
>
> To be more clear:
>
>   If I compile some code on a 32bits host the compiler
>   (C, Fortran or whatever) usually produce 32bits binaries
>
>   If I compile some code on a 64 bits host the compiler
>   (C, Fortran or whatever) usually produce 64bits binaries
>
> So CMake detect the compiler (C; Fortran, ...) and do not care
> about 32/64 bits issue.
>
> Now if YOUR code as 32/64 bits specific zone then you need an appropriate
> macro whose definition may be done by you (in CMakeLists.txt) by testing
> the value of CMAKE_SIZEOF_VOID_P.
>
> Now some platform like Mac OS support multi-arch binaries and if you
> crawl the mail archive you'll find discussion about that.
>
>
> --
> Erk
> Membre de l'April - « promouvoir et défendre le logiciel libre » -
> http://www.april.org
>
>
>
>   


-- 
Eric Pellegrini
Calcul Scientifique
Institut Laue-Langevin
Grenoble, France