[CMake] Dependency problem

[Alexander Neundorf]

On Monday 22 June 2009, pjtr hahn wrote:
> 2009/6/22 Tyler Roscoe <tyler at cryptio.net>:
> > Are you sure it doesn't Just Work if you do it the straightforward way?
>
> Yes I am. I tried all combinations.
>
> If I add the phony_name AND the *.cpp as OUTPUT it will compile on
> every run regardless if the .cpp has been touched by the command or
> not.
> If I only add the phony_name the *.cpp needs a second run to compile.
> If I only add the *.cpp my custom command is only run once.
>
> > If it really doesn't, you could try generating your .cpp to somewhere
> > out of the way and then do cmake -E copy_if_different to get it to the
> > right place. This way, even if your rule updates your .cpp every time,
> > it will be only be copied to the place where the compiler looks for it
> > if it has changed.
>
> This is what I am actually doing in my script that is run by the
> custom command. I leave the *.cpp untouched based on some external
> condition even if the rule is executed at every build.
> This is what I try to achive. Run the custom command at every build,
> check some conditions and based on them update the *.cpp. If the
> update condition is met and the file was touched then recompile.
>
> > But really I think it will just work if you add the relevant
> > OUTPUT/DEPENDS parameters to your custom commands/targets.
>
> No. OUTPUT definitely doesn't work as expected. Adding the *.cpp to
> OUTPUT causes a recompile on every run even if the file was untouched.

Please post an example which shows this issue.
It should really work (and does here).

Alex