Re: [boost] proposal - modularize Boost build system

Subject: Re: [boost] proposal - modularize Boost build system
From: Peter Dimov (lists_at_[hidden])
Date: 2017-06-19 16:32:11

Stefan Seefeld wrote:
>  I know about these tricks (I use something similar to set up my 
> Boost.Python CI environment), but consider them hacks as they don't really 
> solve the fundamental requests, which are:
>
> * I want to be able to build a given Boost library stand-alone, with 
> nothing but the library's repo being checked out. (In other words: 
> prerequisite Boost components should be assumed pre-installed.)

Why is this so important for you? The difference is just one superproject 
shell and one tools/build. Is this a matter of principle, or are there 
technical reasons?

Anyway.

Boost.Build actually supports this use case:

    sudo yum install boost-jam
    sudo yum install boost-build
    git clone --depth=1 https://github.com/boostorg/python
    cd python
    touch Jamroot
    bjam test

The first error here is

    IMPORT error: rule "requires" unknown in module 
"../../config/checks/config"

because we don't have Boost.Config checked out as a sibling here.

When I comment out your use of ../../config/checks/config in test/Jamfile, 
it errors out with

    rule numpy_test unknown

Trying to build with

    bjam build

fails with

    rule py-version unknown

Both of these errors are because these rules don't exist in the 1.53 
python.jam.

So frankly, I'm not sure how do you suggest this needs to be addressed. On 
one hand, you want to use the system Boost.Build, and on the other, your 
Jamfiles depend on features that aren't present in it. This simply cannot 
work, your desires are contradictory.