Re: [boost] boost-install-ing zlib (Was: Re: [Release] Boost 1.70.0 Beta 1 Release Candidate 2)

Subject: Re: [boost] boost-install-ing zlib (Was: Re: [Release] Boost 1.70.0 Beta 1 Release Candidate 2)
From: Peter Dimov (pdimov_at_[hidden])
Date: 2019-03-13 18:26:36

> > I'll need to try and see what happens with <source> in user-config. 
> > Probably nothing good, because one would expect neither <build-name> nor 
> > <tag> to be specified in such a case.
>
> If I remove the check for ZLIB_SOURCE, and just do
>
>     alias boost_zlib : /zlib//zlib ;
>     libraries-to-install += boost_zlib ;
>
> unconditionally in libs/iostreams/build/Jamfile, this is what happens:
>
> - when `using zlib : : <source>C:/Projects/zlib-1.2.11 ;` is in 
> user-config, the default `b2 install` fails because `address-model=32,64 
> variant=debug,release` conflict as all try to build `libz.lib`. When 
> address-model=32 variant=debug is given, `libz.lib` is installed in 
> C:\Boost\lib, and the CMake configuration for boost_zlib correctly points 
> to it.

And if I use

using zlib : : <source>C:/Projects/zlib-1.2.11 <build-name>z32d : 
<address-model>32 <variant>debug ;
using zlib : : <source>C:/Projects/zlib-1.2.11 <build-name>z64d : 
<address-model>64 <variant>debug ;
using zlib : : <source>C:/Projects/zlib-1.2.11 <build-name>z32 : 
<address-model>32 <variant>release ;
using zlib : : <source>C:/Projects/zlib-1.2.11 <build-name>z64 : 
<address-model>64 <variant>release ;

instead, `b2 install --with-iostreams` works as expected. It would be more 
user-friendly if we somehow did automatically apply <tag> to the simple

using zlib : : <source>C:/Projects/zlib-1.2.11 ;

, but zlib.jam is in Boost.Build and the <tag> is in Boost Jamroot. :-/

Either way, a more correct check for whether `boost-install boost_zlib` 
needs to be performed is "whether /zlib//zlib is being built from source", 
but I'm not sure how to express this condition.