Re: [boost] Configuration framework (Was: [Regex] Building Boost.Regexwith ICU)

Subject: Re: [boost] Configuration framework (Was: [Regex] Building Boost.Regexwith ICU)
From: Vladimir Prus (vladimir_at_[hidden])
Date: 2010-09-22 10:48:29

John Maddock wrote:

>> I think the important question here is what mode do we want.
>>
>> One mode is where you have a feature test as a .cpp file which tries to
>> use
>> "important" functions from a library, and then declare a Boost.Build
>> metatarget that builds that .cpp and links to a library. In this case,
>> if you modify the .cpp, the regular dependency checking will rebuild
>> the test. Also, the test will be repeated if the system headers for the
>> library change -- a particularly nifty example is including
>> "whatever/version.hpp" and making some decisions based on version.
>> Some changes to the way libraries are linked will allow the test to be
>> rebuilt when a system library itself is modified.
>>
>> Another mode is where configure checks tries to compile or link something,
>> and caches the result. One can remove the cache and run all checks again,
>> but otherwise the system assumes nothing changes.
>>
>> I, personally, is not very happy with the second mode as implemented in
>> cmake. However, it might be that the best mode depends on the nature of
>> the
>> test, and we need to support both. Comments?
> 
> I'm not happy with the second mode either - if something in the source
> changes then the test should definitely be rebuilt - most users will
> presumably only build the thing once anyway during an install so it won't
> make any difference to them?

Most users -- yes. However, there are also developers, and I am surely
not happy about the existing build system that require to basically
reconfigure afresh after each major change.

- Volodya