[CMake] configure_file without continuous re-build

[Michael Jackson]

you shouldn't have to do that. There are multitudes of projects that  
do exactly what you are doing and don't have continuous rebuilds. Now,  
having said that I am _assuming_ that osconfig.h.in is NOT being  
changed, generated, updated or in any way changed? osconfig.h.in being  
changed would cause "configure_file()" to re-run which will regenerate  
the osconfig.h file.

   Early in the HDF5/CMake port we were doing exactly that which  
caused HDF5 to be rebuilt just about completely because the "H5conf.h"  
file was always being generated at cmake time.

_________________________________________________________
Mike Jackson                  mike.jackson at bluequartz.net
BlueQuartz Software                    www.bluequartz.net
Principal Software Engineer                  Dayton, Ohio

On Jan 12, 2010, at 3:51 PM, Tyler Roscoe wrote:

> On Tue, Jan 12, 2010 at 02:09:36PM -0600, Daniel Blezek wrote:
>> CONFIGURE_FILE(${DCMTK_SOURCE_DIR}/osconfig.h.in
>>               ${DCMTK_BINARY_DIR}/include/dcmtk/config/osconfig.h)
>>
>> However, every time I touch a CMake file, ³osconfig.h² is  
>> regenerated,
>> causing nearly the entire library to re-build because of  
>> dependancies.  Is
>> this a good/proper/recommended way to guard against regeneration of  
>> the
>> file?
>
> You could configure_file() to a temporary location, then
> 'cmake -E copy_if_different' from the temp location to the real
> location. This way, the real osconfig.h is only updated (and the
> dependent parts of the build are re-compiled) if something has  
> changed.
>
> tyler
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