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Subject: Re: [boost] Boost CMake support - Request for Comment
From: Edward Diener (eldiener_at_[hidden])
Date: 2018-10-16 14:12:40

On 10/16/2018 3:34 AM, Alexander Grund via Boost wrote:
>> For Predef
>> <> with
>> documentation for usage here
>> <>.
>> For Config <>
>> and documentation for that here
>> <>.
> Thanks. Seeing this I approximate the work required to convert the
> checks of Config to ~1h, maybe 2h. Usage would be:
>   include(BoostConfigFeatures)
>   if(BOOST_FEATURE_cxx11_local_class_template_parameters)
>     add_executable(...)
>   endif()

Programmers are notorious for estimating the work to do any programming
as about an order of magnitude less than it really takes <g>.

> Some bike-shedding required:
> - Name for the CMake file that contains this

Anything reasonable with 'config' in the name for config and 'predef' in
the name for predef.

> - Naming scheme for the results of the checks (the variable in the "if")

As close as possible, using CMake naming conventions, to the name in
config or predef.

> - Eagerly test all or on demand:

What is the difference in CMake terms ? In Boost Build I am fairly sure
the checks are done on demand, and usually involves some sort of
compile/build/run/test-result cycle which would make pre-testing all
checks in a library, and holding the result for further inquiry, pretty

>   boost_config_has(RESULT cxx11_local_class_template_parameters)
>   if(RESULT) add_executable(...) endif()
> Similar for predef:
>   include(BoostPredefCheck)
>   boost_predef_check(RESULT "BOOST_OS_WINDOWS != 0" "BOOST_OS_VMS != 0")
>   if(RESULT) add_executable(...) endif()
> Work is about the same and yes some checks can be omitted (e.g.
> boost_predef_check(RESULT "BOOST_OS_WINDOWS != 0") --> RESULT==WIN32
> standard CMake variable)

Even if there is a standard CMake variable it would be worthwhile to
have the check so that libraries which use the check can use the same
syntax throughout.

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