[CMake] cmake on Windows x64

[Yuri Timenkov]

The 32 vs 64 bit switch based on pointer size is not sufficient. To be 100%
correct you shall be able to differentiate between x86_64 and IA-64
(However I think it's quite rare case). And to me personally condition with
target architecture looks better than CMAKE_CL_64 or checking the size of
pointer.

I think the "... Win64" generator is a bit confusing because what it
actually does - is cross-compilation however cross-compilation requires
more variables to be set properly.

I also need an advice on how to deal with package configs. They've proven
to be very convenient but how to differentiate when you have single header
location and 32- and 64-bit libraries?


On Mon, Oct 15, 2012 at 9:37 PM, John Drescher <drescherjm at gmail.com> wrote:

> > Having CMAKE_SYSTEM_PROCESSOR be "x86" for a 64-bit build is very
> inconvenient when detecting machine-dependent compiler flags, constructing
> directory names for outputs based on configuration, configuring third party
> search directories, etc.  It's always possible to work around (among other
> things, one can consult the generator string for Visual Studio builds,
> though not for MinGW builds) but that doesn't mean it shouldn't be better
> behaved - it's entirely reasonable to assume that CMAKE_SYSTEM_PROCESSOR
> should be the target processor for the build, especially so that you can
> have similar behavior on Windows, Linux, and Mac.  Though as previously
> discussed I also have the opposite problem on Linux when compiling for
> 32-bit CPU on 64-bit OS.
>
>
> I see. I have always compared the size of the pointer for this..
>
> John
>
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