Re: [PATCH 0/4] mingw: prevent external PERL5LIB from interfering

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Oct 31, 2018, 11:04 UTC
Message-ID: <nycvar.QRO.7.76.6.1810311151170.4546@tvgsbejvaqbjf.bet>
In-Reply-To: <xmqqtvl2ye3b.fsf@gitster-ct.c.googlers.com>

Hi Junio,

On Wed, 31 Oct 2018, Junio C Hamano wrote:

Show 17 quoted lines

> "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
> writes:
> 
> > An alternative approach which was rejected at the time (because it
> > interfered with the then-ongoing work to compile Git for Windows using
> > MS Visual C++) would patch the make_environment_block() function to
> > skip the specified environment variables before handing down the
> > environment block to the spawned process. Currently it would interfere
> > with the mingw-utf-8-env patch series I sent earlier today
> > [https://public-inbox.org/git/pull.57.git.gitgitgadget@gmail.com].
> 
> So the rejected approach that was not used in this series would
> interfere with the other one, but I do not have to worry about it
> because this series does not use that approach?  I had to read the six
> lines above twice to figure out that it essentially is saying "I
> shouldn't care", but please let me know if I misread the paragraph and I
> need to care ;-)

Well, you might want to worry about it. Or not.

The approach taken by this patch series is to call `unsetenv()` for the variable names listed in `core.unsetenvvars` (if any), just before spawning off the first process (if any).

What I meant by this comment in the cover letter is that I thought about doing it differently. We already have a perfectly fine function called `make_environment_block()` that takes a "deltaenv", and then constructs a new environment block from the current environment plus deltaenv. And this would be an obvious alternative place to "unset" the variables, as this function is only called just before spawning new processes.

I was weighing both options, and both back then as right now, there are other patches in flight that conflict with the second approach, so the first approach is what I went with.

From a purely aesthetic point of view, the second approach looks nicer, as it really only affects the spawned processes (and not the current one), and it allows for changing the list between spawning processes.

But to do it right, I would also have to use a hash set, and it would complicate the code of `make_environment_block()` even further. And it sounds a bit like overkill to me, too.

So I sided with the approach presented in the current revision of the patch series, but I wanted to describe the other approach in case you (or other reviewers) have a different opinion.

Show 6 quoted lines

> > While at it, this patch series also cleans up house and moves the
> > Windows-specific core.* variable handling to compat/mingw.c rather
> > than cluttering environment.c and config.c with things that e.g.
> > developers on Linux do not want to care about.
> 
> Or Macs.

Or macOS. Or FreeBSD. Or Irix. Or any other, that's right ;-)

Traditionally, we did not really care all that much about platforms other than Linux, though, which is what made me write what I wrote. Having said that, I get the impression that this is changing slowly. The benefits are pretty clear, too. After all, it was a *Windows* build failure recently that let Peff identify and fix a *non-Windows* bug...

> When I skimmed this series earlier, I found that patches 2 & 3 sensibly
> implemented to achieve this goal.

Thanks! Dscho

Show 25 quoted lines

> 
> >
> > Johannes Schindelin (4):
> >   config: rename `dummy` parameter to `cb` in git_default_config()
> >   Allow for platform-specific core.* config settings
> >   Move Windows-specific config settings into compat/mingw.c
> >   mingw: unset PERL5LIB by default
> >
> >  Documentation/config.txt     |  6 ++++
> >  cache.h                      |  8 -----
> >  compat/mingw.c               | 58 +++++++++++++++++++++++++++++++++++-
> >  compat/mingw.h               |  3 ++
> >  config.c                     | 18 ++++-------
> >  environment.c                |  1 -
> >  git-compat-util.h            |  8 +++++
> >  t/t0029-core-unsetenvvars.sh | 30 +++++++++++++++++++
> >  8 files changed, 109 insertions(+), 23 deletions(-)
> >  create mode 100755 t/t0029-core-unsetenvvars.sh
> >
> >
> > base-commit: 4ede3d42dfb57f9a41ac96a1f216c62eb7566cc2
> > Published-As: https://github.com/gitgitgadget/git/releases/tags/pr-62%2Fdscho%2Fperl5lib-v1
> > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-62/dscho/perl5lib-v1
> > Pull-Request: https://github.com/gitgitgadget/git/pull/62
>