[CMake] copy_if_different on build

[Matthew Woehlke]

On 2013-03-29 15:15, Skippy VonDrake wrote:
> I'm using:
>    execute_process(COMMAND ${CMAKE_COMMAND}  -E  copy_if_different
> <some-file>  <some-dest-dir>)
>
> Should the file be copied when:
>     the file has changed AND a build is executed?
>     Or
>     the file has changed AND CMakeLists.txt has changed AND a build is executed?
>
> Only the 2nd method (when the CMakeLists.txt file is touched) results in the
> changed file being copied.
>
> I'd expect the 1st method to also cause a file copy.
> If this assumption is wrong please tell me why.

execute_process is a configure step. It does not create build rules and 
will ONLY execute when CMake is run.

If you want to create a build rule, use add_custom_command or 
add_custom_target instead.

Anyway, the above is silly; if you really only wanted the file copied at 
cmake time, you should instead use configure_file(... COPY_ONLY) :-) 
rather than unnecessarily invoking an extra process.

-- 
Matthew