[CMake] [Insight-developers] 64 bit build detection

[David Cole]

CMake does not warn.
And actually, I think I have to back-track on my statement a little bit.

Whether or not a TRY_COMPILE "works" for a multiple arch / config build
*depends* entirely on what you are trying to compile and what result you are
expecting to get out of it. If you do a try compile on some code to detect
the presence of a function, for example, that should work fine on a
universal binary build (presuming the function you're trying to link against
is present in universal binary form in the library it lives in...).

The thing that won't work on a multiple arch/config build is trying to
detect the size of something or the presence/absence of something where the
thing you're trying to measure is different in the different archs /
configs. If it's uniform across all archs/configs then you can measure it
and get an answer that makes sense for all archs/configs. If not, then you
can't.

Does that make sense?

So... CMake does not warn because it does not know whether what you are
attempting to measure is valid or not. It's up to you to "do the right
thing" in these sorts of situations.

You already know that if you are building a universal binary with both
32-bit and 64-bit architectures in it that it makes no sense to "measure"
the size of "void*" at CMake time. You know this because you know there is
more than one answer depending on which one runs.


Hope this clarifies things even further, (rather than muddying anybody's
waters...)

David


On Thu, Jun 11, 2009 at 6:56 PM, Sean McBride <sean at rogue-research.com>wrote:

> On 6/11/09 5:25 PM, David Cole said:
>
> >TRY_COMPILE works fine for cross compiles, just not for *mutiple
> >configs/architectures "simultaneously"* compiles...
>
> Thanks for the clarification, that language is clearer.
>
> Does CMake detect and warn in such cases?  (it is after all the common
> case on OS X.)
>
> Cheers,
>
> --
> ____________________________________________________________
> Sean McBride, B. Eng                 sean at rogue-research.com
> Rogue Research                        www.rogue-research.com
> Mac Software Developer              Montréal, Québec, Canada
>
>
>
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