Need Help with python extension builder

[SirVer]

Hi,

I am trying to build a Builder for python extensions and I run into
some difficulties. The basic idea is to build *.c -> shared libraries,
but python defines via distutils.sysconfig.get_config_vars() precisely
which c compiler, which commands and flags should be used for compile,
link and so on. What I want to do is to use all of the existing c
infrastructure for dependency handling but run precisely the cmdline
that python provides to compile and link. I tried to use guess_shared
and overwrite some of it's calls, but guess_shared always changes
stuff around: dst "blah" becomes "libblah.dylib" which is not valid
for python (it should be "blah.so").

I am a bit lost and I have no idea how to properly implement this.
Could someone point me to a good start?

Cheers,
Holger

[Erick Tryzelaar]

Hm, well the first way I could see doing this is you could run an
external python shell to get those variables. This could be a bit
ugly, as in:

fbuildroot.py:

import fbuild.builders.c
import pickle

def build(ctx):
stdout, stderr = ctx.execute((
'/opt/local/bin/python2.6',
'-c',
'import distutils.sysconfig, pickle; '
'print pickle.dumps(distutils.sysconfig.get_config_vars())'
), stdout_quieter=1)

static = fbuild.builders.c.guess_static(ctx,
macros=pickle.loads(stdout))

static.build_exe('foo', ['foo.c'])

And I'll add some hooks in order to replace the .dylib to .so
extension. Theoretically the compiler shouldn't matter since c has a
standard calling convention. However, it's possible to set specific
executables, by explicitly picking the builder, and setting the
executable like:

import fbuild.builders.c.gcc
fbuild.builders.c.gcc.shared(ctx, exe='/usr/bin/gcc', ...)

Do you know of other restrictions though?

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[SirVer]

Hi,

On 27 Dez., 02:11, Erick Tryzelaar <erick.tryzel...@gmail.com> wrote:
> Hm, well the first way I could see doing this is you could run an
> external python shell to get those variables. This could be a bit
> ugly, as in:
>
> fbuildroot.py:
>
> import fbuild.builders.c
> import pickle
>
> def build(ctx):
>     stdout, stderr = ctx.execute((
>         '/opt/local/bin/python2.6',
>         '-c',
>         'import distutils.sysconfig, pickle; '
>         'print pickle.dumps(distutils.sysconfig.get_config_vars())'
>     ), stdout_quieter=1)
>
>     static = fbuild.builders.c.guess_static(ctx,
>         macros=pickle.loads(stdout))
>
>     static.build_exe('foo', ['foo.c'])
>

That's actually exactly how I did it. It didn't completly come through
because some hooks are missing

> And I'll add some hooks in order to replace the .dylib to .so
> extension. Theoretically the compiler shouldn't matter since c has a
> standard calling convention. However, it's possible to set specific
> executables, by explicitly picking the builder, and setting the
> executable like:

I tried this. I would also need complete control over how the library
is build (that is, he shouldn't use ar,
but use gcc for everything. And he shouldn't add -dynamic or
something, python dictates which switches to use)

> Do you know of other restrictions though?

When can you add those hooks? I'd really like to work on it while I am
on the conference I am currently attending ;)

Cheers,
Holger

[Erick Tryzelaar]

On Dec 27, 2009, at 12:25 PM, SirVer <sir...@gmx.de> wrote:

When can you add those hooks? I'd really like to work on it while I am
on the conference I am currently attending ;)

Hi Holger! Sorry I've been slow to reply, I'm off on vacation for the next little bit. I've already started working on the hooks, and I think I'll have some time tomorrow mornig to get them done. Hopefully that'll work for you.   

Cheers,
Holger

[Erick Tryzelaar]

On Sun, Dec 27, 2009 at 9:25 AM, SirVer <sir...@gmx.de> wrote:
>
> I tried this. I would also need complete control over how the library
> is build (that is, he shouldn't use ar,
> but use gcc for everything. And he shouldn't add -dynamic or
> something, python dictates which switches to use)

I pushed out my changes. Now you can write:

def build(ctx):
stdout, stderr = ctx.execute((
'/opt/local/bin/python2.6',
'-c',
'import distutils.sysconfig, pickle; '
'print pickle.dumps(distutils.sysconfig.get_config_vars())'
), stdout_quieter=1)

shared = fbuild.builders.c.guess_shared(ctx,
macros=pickle.loads(stdout),
lib_prefix='',
lib_suffix='.so')

shared.build_lib('foo', ['foo.c'])