Re: Build dirs and in-path features

From: David Abrahams (dave_at_[hidden])
Date: 2004-12-14 10:39:05

Vladimir Prus wrote:
> On Saturday 11 December 2004 14:51, Zbynek Winkler wrote:
> 
>> >I think i actually know the answer, but it's only because I understand
>> >how Scons works -- what you've written above seems pretty disconnected.
>>
>> It means that if you switch compilers, add/remove flags etc. the files
>> that should be rebuilt are rebuilt. For boost build this is true only to
>> certain extent - only if you add feature that is represented in the
>> build path. More on this at the end....
> 
> Yes, SCons has an advantage here because of MD5 signatures. Somebody has a 
> similar setup with jam, though. (Classic Jam + patches, not bjam + 
> Boost.Build).
> 
>> >Building into the current directory has some major disadvantages for
>> >Boost developers who are trying to write multiplatform, multi-compiler
>> >software.
>>
>> Sorry for not being clear on this either. I do not propose to build to
>> the current directory all the time. I just think that it is very very
>> nice to have the *option* to build to directories specific to
>> variant/compiler but it would be IMHO better not to be forced to it.
> 
> Should this option be per-project, or per-user. And what do to with old 
> objects when you switch directory layout?
> 
> We probably can make all feature "non-symmetric". So, if you're builting with 
> a "default" toolset, it's not shown in path at all. Say, building with msvc 
> will produce
> 
> bin/debug/a
> 
> building with gcc will produce
> 
> bin/gcc/debug/a
> 
> But it will be inconvenient for persons with multiple toolsets. We're back to 
> question on how the option is specified.

We could decide that the toolset feature has a default value (the result
of all the xxx-config.jam files) when none is specified on the
command-line. That's not bad, actually.

> It's http://zigzag.lvk.cs.msu.su:7814/scarab/issues/id/BB37
> Basically, if my_cool_app depends on boost, then bjam --clean will remove not 
> my my_cool_app objects, but also all of boost.

Oh. Not a huge deal IMO.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com