Hi

After days of failing to add a few new simple features to gbuild, I've now
reached my limits, and have begun experimenting with the SCons build system
instead.

It's starting to work. Having ported some of gbuild.mk, LinkTarget.mk and
platform/freebsd.mk to SCons, as well as a module's local gbuild files, I
can now compile files and (badly) link them into libraries, and clean the
build.

SCons is an advanced next-generation build system like gbuild, with high
level declarative syntax in Python, support for multiple modules that build
in parallel, header dependencies, file change detection through MD5 sums of
contents instead of timestamps so rebuilds are faster, etc. It builds C,
C++, Objective C, Java, Fortran, D, the sorely necessary Flex and Yacc that
gbuild doesn't support. It supports tons of platforms and compilers,
including OS/2. It's maintainable and usable, can print debugging info such
as dependency trees, and is generally pleasant to work with. We've
discussed it before on this list, but I never got to trying it until now.

Virtually everything gbuild does, is already done by SCons, and often done
much better. The syntax for SCons files is similar/related to gbuild's
syntax, so an automated conversion from gbuild to SCons might even be
possible.

So far, I have defines, includes and C[XX]FLAGS working. I've structured it
a bit better, with platform-specific files in classes that only provide
variables to slot in higher up, instead of one giant set of globally
mutable global variables like in gbuild. Linking still needs a bit of work.
Windows is next on the list, as Cygwin will be the ultimate test of whether
we can use it.

I am very hopeful. SCons has a long history and is used by other projects,
while only OO.o derivatives use gbuild. It's well documented. It supports
features we need which gbuild doesn't, like library version names and
flex/yacc. It's supposed to work on Windows, both inside and outside of
Cygwin and could help us build without Cygwin some day. It supports many
versions of Visual Studio and could help us in upgrading to a new one. We
will need to add custom builders to SCons for our custom file formats like
IDL, but it's just Python, not my favorite language but infinitely better
than GNU make.

It would help if someone could review my changes, as I am not very familiar
with Python and there might be better ways to write some of the code. I'll
post a patch for review after some further development.

Thank you
Damjan

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