Re: [Boost-build] prototyping alternative Boost.Build syntax

Subject: Re: [Boost-build] prototyping alternative Boost.Build syntax
From: Stefan Seefeld (stefan_at_[hidden])
Date: 2016-10-31 15:56:38

On 31.10.2016 12:29, Steven Watanabe wrote:
>> When building with MSVC, somewhere in the process one of these
>> "vcvars32.bat" scripts is read in to set up environment variables that
>> are later used during the invocation of "cl.exe" etc. As I suppose that
>> script isn't read in on each invocation of an action that calls one of
>> the MSVC tools, I suppose some form of environment sharing has to be used.
>> Am I wrong ?
>>
>   vcvars32.bat is called on every invocation of
> the compiler.  There is no environment sharing.

Is there a way for me to convince you (or someone else maintaining the
bjam C code) to add support for environment sharing ? I understand that
this may not be relevant for the current version of Boost.Build (which
works around the current limitation), but for any future work this would
be very useful ! (The bjam_define_action() and bjam_call() functions
could take an optional extra argument that would be the environment to
share. This would make it much easier to design the Python layer...)

> (Actually, Boost.Build writes its own version
> of vcvars32.bat because on some version of msvc,
> the provided vcvars32.bat is quite slow.  However,
> for your purposes, this detail doesn't really matter.
> The point is that the environment must be set
> up from scratch every time.)

SCons introduces the notion of a "construction environment"
(http://scons.org/doc/HTML/scons-user.html#sect-construction-environments),
which I find quite elegant, and having the ability to define something
like that in bb3 would be very useful.

Thanks,
        Stefan

-- 
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