[PATCH 3/5] buildman: Support building within a Python venv

[Simon Glass]

Hi Tom,

On Thu, 20 Jun 2024 at 08:32, Tom Rini <trini at konsulko.com> wrote:
>
> On Thu, Jun 20, 2024 at 07:19:35AM -0600, Simon Glass wrote:
>
> > The Python virtualenv tool sets up a few things in the envronment,
> > putting its path first in the PATH environment variable and setting up
> > a sys.prefix different from the sys.base_prefix value.
> >
> > At present buildman puts the toolchain path first in PATH so that it can
> > be found easily during the build. For sandbox this causes problems since
> > /usr/bin/gcc (for example) results in '/usr/bin' being prepended to the
> > PATH variable. As a result, the venv is partially disabled.
> >
> > The result is that sandbox builds within a venv ignore the venv, e.g.
> > when looking for packages.
> >
> > Correct this by detecting the venv and adding the toolchain path after
> > the venv path.
> >
> > Signed-off-by: Simon Glass <sjg at chromium.org>
>
> Why are we using PATH at all in this case? Shouldn't we just be setting
> CROSS_COMPILE=/full/path/to/the/prefix ?

This is the -p option to buildman. The original commit was:

commit bb1501f2c22c979961b735db775605cccedd98f6
Author: Simon Glass <sjg at chromium.org>
Date:   Mon Dec 1 17:34:00 2014 -0700

    buildman: Add an option to use the full tool chain path

    In some cases there may be multiple toolchains with the same name in the
    path. Provide an option to use the full path in the CROSS_COMPILE
    environment variable.

    Note: Wolfgang mentioned that this is dangerous since in some cases there
    may be other tools on the path that are needed. So this is set up as an
    option, not the default. I will need test confirmation (i.e. that this
    commit fixes a real problem) before merging it.

As to why we don't always do this, well that is back in the mists of
time, 10 years ago.

BTW, this is raising a point ("let's change the behaviour") separate
from the goal of this commit, which is to fix a problem with venv,
albeit that if we made -p the only option, then we could potentially
drop all PATH changes. Perhaps toolchains are built differently now,
such that they always invoke their tools using the same prefix and
dir?

Regards,
Simon