Re: [scons-devel] auto-configuration plans

Bram Moolenaar said:
> From the configure run you might get several variable values, such as
> $CFLAGS and $LIBS.  But different parts of the build will want to use
> different values.  For example building a C source file with the default
> $CFLAGS instead of using the result from configure.
>
> I'm sure there are various ways to access both the values from before
> the configure checks and the values that configure detected.  The
> configure run may use different variables for different config tests.
> But you probably don't want to use both a $LIBS and a $CONFIG_LIBS
> variable.  To me it sounds more logical to have a $LIBS in two scopes
> (or two environments for SCons).

I understand now.  Under SCons you can just call env.Copy() before
starting the configure.  I actually setup a seperate environment for each
Program/Library/Object that needs its own configuration.

> It's not this simple.  Actions defined in the recipe for building and
> compiling need to be used for ":program".  These include Aap commands,
> thus can't be directly executed by the SCons engine.  The source files
> may have attributes (e.g., to automatically download them when needed).
> I think the SCons build engine would have to be expanded quite a bit to
> support all the Aap features.

Ok, this is about to all be personal bias since I have never read through
your code.  But I think it would be possible to provide all your
functionality through hooks into your existing code.  If one of the files
in the former example needed to be downloaded from somewhere you could do:

env.Command(target="foo.c", source="ftp://someftp.com/source/foo.c", \
  action=AAP.DownloadFunction)

Imagine that AAP.DewnloadFunction is a python function that can take the
given source string and environment to produce the file.  This would add
the download information to the Node in the SCons dependancy tree.  You
could have this call happen before or after the Program one.  The whole
node tree is maintained in the background.

> I don't have time to work in this, I'm afraid.  But if someone can show
> us how the SCons build engine could be used in Aap and that it has
> advantages, I will certainly consider making Aap work that way.

The advantages would be that we wouldn't be duplicating our efforts.  That
is probably about it.

Thank you.
  -- David Snopek

Satellite Computing Solutions, LLC


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