On Mac OS X one shouldn't do this kind of detection during configure
step, because as has been mentioned a single file can be compiled
multiple times for different architectures during one single compiler
invocation. The size of void* and even endianness can change. It is
preferable to have a central config.h.in (or similar) containing
something like this:
#if defined(__APPLE__)
# if defined(__i386__)
# undef HAVE_64_BIT
# undef HAVE_BIG_ENDIAN
# elif defined(__ppc__)
# undef HAVE_64_BIT
# define HAVE_BIG_ENDIAN
# elif defined(__x86_64__)
# define HAVE_64_BIT
# undef HAVE_BIG_ENDIAN
# elif defined(__ppc64__)
# define HAVE_64_BIT
# define HAVE_BIG_ENDIAN
# else
// oops
# error "Unknown architecture!"
# endif
#else
# cmakedefine HAVE_64_BIT
# cmakedefine HAVE_BIG_ENDIAN
#endif
On NOT APPLE platforms you do the normal thing in your CMakeLists.txt:
if( NOT APPLE )
# check 64 bit
if( CMAKE_SIZEOF_VOID_P EQUALS 4 )
set( HAVE_64_BIT 0 )
else( CMAKE_SIZEOF_VOID_P EQUALS 4 )
set( HAVE_64_BIT 1 )
endif( CMAKE_SIZEOF_VOID_P EQUALS 4 )
# check endianness
include( TestBigEndian )
test_big_endian( HAVE_BIG_ENDIAN )
if( HAVE_BIG_ENDIAN )
set( HAVE_BIG_ENDIAN 1 )
else( HAVE_BIG_ENDIAN )
set( HAVE_BIG_ENDIAN 0 )
endif( HAVE_BIG_ENDIAN )
endif( NOT APPLE )
# configure config.h
configure_file( ${CMAKE_SOURCE_DIR}/config.h.in ${CMAKE_BINARY_DIR}/
config.h )
include_directories( ${CMAKE_BINARY_DIR} )
HTH
Michael
On 12. Jun, 2009, at 15:01, David Cole wrote:
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 <s...@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 s...@rogue-research.com
Rogue Research www.rogue-research.com
Mac Software Developer Montréal, Québec, Canada
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
Please keep messages on-topic and check the CMake FAQ at:
http://www.cmake.org/Wiki/CMake_FAQ
Follow this link to subscribe/unsubscribe:
http://www.cmake.org/mailman/listinfo/cmake
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
Please keep messages on-topic and check the CMake FAQ at:
http://www.cmake.org/Wiki/CMake_FAQ
Follow this link to subscribe/unsubscribe:
http://www.cmake.org/mailman/listinfo/cmake
