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

[Alexander Neundorf]

On Thursday 11 June 2009, Sean McBride wrote:
> On 6/11/09 3:00 PM, Michael Jackson said:
> >-- CMAKE_SIZEOF_VOID_P: 4  <============ THIS IS WRONG FOR X64 builds
>
> Yeah, but gcc on 10.5 and earlier defaults to building 32 bit.  If you
> want 64 bit you need to pass '-arch x86_64' (or ppc64).  Or in the case
> of CMake, use CMAKE_OSX_ARCHITECTURES (or whatever its called).
>
> But if you use multiple architectures, like i386 _and_ x86_64, then each
> arch can and does have a different size void*.  Now sure what CMake does
> there, hopefully warns or errors.
>
> Always best to avoid TRY_RUNs and I guess TRY_COMPILES too for Universal
> Binaries/cross compilation.

This is from CheckTypeSize.cmake:

SET(CMAKE_CHECKTYPESIZE_FIRST_RESULT "FIRST_LOOP")
FOREACH(info ${CMAKE_CHECKTYPESIZE_STRINGS})
  IF("${info}" MATCHES ".*INFO:sizeof\\[0*([^]]*)\\].*")
    STRING(REGEX REPLACE ".*INFO:sizeof\\[0*([^]]*)\\].*" "\\1" 
${VARIABLE} "${info}")
  ENDIF("${info}" MATCHES ".*INFO:sizeof\\[0*([^]]*)\\].*")
  IF("${CMAKE_CHECKTYPESIZE_FIRST_RESULT}" STREQUAL "FIRST_LOOP")
    SET(CMAKE_CHECKTYPESIZE_FIRST_RESULT "${${VARIABLE}}")
  ENDIF("${CMAKE_CHECKTYPESIZE_FIRST_RESULT}" STREQUAL "FIRST_LOOP")
  IF(NOT "${CMAKE_CHECKTYPESIZE_FIRST_RESULT}" STREQUAL "${${VARIABLE}}")
    MESSAGE(SEND_ERROR "CHECK_TYPE_SIZE found different results, consider 
setting CMAKE_OSX_ARCHITECTURES or CMAKE_TRY_COMPILE_OSX_ARCHITECTURES to one 
or no architecture !")
  ENDIF(NOT "${CMAKE_CHECKTYPESIZE_FIRST_RESULT}" STREQUAL "${${VARIABLE}}")

ENDFOREACH(info ${CMAKE_CHECKTYPESIZE_STRINGS})

So if you are building universal binaries, and if check_type_size() finds more 
than one result, and if these results differ, then there should be an error 
generated.
I can't test that here, I don't have a Mac at hand.

Alex