[CMake] Naive (stupid?) question

[Carminati Federico]

Alexander,
  thanks for your explanation. I think we are introducing fake dependencies in the way we include directories. We will have to look into this. I was not questioning cmake, for me it is clear that the problem is on our side. I also think we are abusing the configure_file comamnd using it to copy files instead of introducing some real dependencies. Some cleanup is needed.... Best, 

Federico Carminati
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On 17 Feb 2011, at 18:12, Alexander Neundorf wrote:

> On Thursday 17 February 2011, Dominik Szczerba wrote:
>> I am also sometimes surprised by the radius of needed re-compilation
>> in my complex project... I think CMake tries to be on the safe side
>> and just regenerates everything that might have been affected. 
> 
> From the experiences in KDE and at work, I haven't seen anything being 
> unnecessarily being recompiled for a long time (I think the last time I saw 
> something unnecessary being built again was in summer 2006).
> 
> When a include dir changes, everything below it will be rebuilt. The same for 
> anything else which changes the compile flags.
> If only your link command changes, the stuff will only be linked again.
> 
> CMake takes great care to ensure only the necessary stuff will be rebuilt: it 
> uses copy-if-changed semantics for creating the Makefiles, the Makefiles are 
> split in parts in such a way that as mentioned above, if only linking has 
> changed, then there are separate files which contain only the linking 
> commands, etc.
> 
> Most probably you really have the dependencies which cause a rebuild.
> 
> Or maybe something is wrong with your (networked ?) filesystem and the 
> timestamps. I have seen that, unncessary recompiles on a network filesystem, 
> which was most probably caused by filesystem issues.
> 
> Alex