[CMake] file dependency not working in external projects

[hex]

hello Eric Doenges,

You are correct. This has been given me headaches.

Setting BUILD_ALWAYS to TRUE gives the desired behaviour.


Thank you


On 24/09/2019 14:59, Eric Doenges wrote:
>
> You're probably missing the BUILD_ALWAYS option to ExternalProject_Add:
>
> |BUILD_ALWAYS <bool>|
>     Enabling this option forces the build step to always be run. This
>     can be the easiest way to robustly ensure that the external
>     project’s own build dependencies are evaluated rather than relying
>     on the default success timestamp-based method. This option is not
>     normally needed unless developers are expected to modify something
>     the external project’s build depends on in a way that is not
>     detectable via the step target dependencies (e.g. |SOURCE_DIR| is
>     used without a download method and developers might modify the
>     sources in |SOURCE_DIR|).
> Am 24.09.19 um 15:23 schrieb hex:
>> hello,
>>
>> I have a problem with a build step.
>>
>> The following command is run every time somefile changes:
>>
>> add_custom_command( OUTPUT out.put
>>     COMMAND touch out.put
>>     DEPENDS somefile.txt
>> )
>>
>> add_custom_target( sometarget DEPENDS out.put )
>>
>>
>> I move this snippet inside an external project (with 
>> ExternalProject_Add) and the custom command is only run once at build.
>>
>> I am using absolute path to somefile, the command is not rebuild 
>> changing somefile.
>>
>> I am using Gnu make generator and build with make all
>>
>>
>> What am I missing?
>>
> -- 
>
> *Dr. Eric Dönges*
> Senior Software Engineer
>
> MVTec Software GmbH | Arnulfstr. 205 | 80634 Munich | Germany
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