distutils should respect the LIBS configure env var

[collinwinter]

BPO	5572
Nosy	@tarekziade, @merwok, @zooba
Files	distutils_libs.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/merwok'
closed_at = <Date 2021-02-03.18:29:09.980>
created_at = <Date 2009-03-26.19:16:51.286>
labels = ['type-bug', 'library']
title = 'distutils should respect the LIBS configure env var'
updated_at = <Date 2021-02-03.18:29:09.980>
user = 'https://bugs.python.org/collinwinter'

bugs.python.org fields:

activity = <Date 2021-02-03.18:29:09.980>
actor = 'steve.dower'
assignee = 'eric.araujo'
closed = True
closed_date = <Date 2021-02-03.18:29:09.980>
closer = 'steve.dower'
components = ['Distutils']
creation = <Date 2009-03-26.19:16:51.286>
creator = 'collinwinter'
dependencies = []
files = ['13422']
hgrepos = []
issue_num = 5572
keywords = ['patch', 'needs review']
message_count = 15.0
messages = ['84199', '84213', '84214', '84215', '87128', '87143', '138448', '138460', '138528', '138535', '138916', '138958', '139112', '139119', '386417']
nosy_count = 8.0
nosy_names = ['collinwinter', 'jyasskin', 'tarek', 'eric.araujo', 'rpetrov', 'Arfrever', 'alexis', 'steve.dower']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue5572'
versions = ['Python 3.5']

[collinwinter]

If you pass LIBS to ./configure (as in "LIBS=-lgcov ./configure"),
distutils ignores this when building extension modules, which breaks
when using certain gcc options which require certain libraries (I'm
thinking of -fprofile-generate). The attached patch remedies this.

[rpetrov]

bpo-5060 address this

[collinwinter]

The patch attached to bpo-5060 seems very tightly focused on a problem
with gcc FDO. This is a more general patch that solves the problem of
distutils ignoring LIBS.

[rpetrov]

The LIBS contain all module dependent libraries, libpython is linked
with LIBS, modules are linked with libpython.
May be I miss something but I could not found why distutils has to use
LIBS to link a module.

[tarekziade]

May be I miss something but I could not found why distutils
has to use LIBS to link a module.

It doesn't right now, but depending on the extension you want to build,
you might want to configure it and make sure it is passed to the compiler.

About the patch:

is there a particular reason why you have changed the call to
'set_library' into calls to 'add_library' in build_ext in your patch ?

[collinwinter]

2009/5/4 <"Tarek Ziadé <report@bugs.python.org>"@psf.upfronthosting.co.za>:

About the patch:

is there a particular reason why you have changed the call to
'set_library' into calls to 'add_library' in build_ext in your patch ?

Yes. It seems like the proper thing to do is to merge the global LIBS
and the module-specific libraries (via add_library()), rather than
having one override the other (set_library()).

[merwok]

Reclassifying as a feature request for the packaging module. The distutils docs don’t say using LIBS is supported and there aren’t many people asking for it on this bug report.

[collinwinter]

This wasn't so much a feature request as a request for review. I had already implemented the necessary changes and provided a patch.

We found this change necessary when working on Unladen Swallow.

[merwok]

This wasn't so much a feature request as a request for review.
From a tracker process viewpoint, any report is a bug, a feature request or a doc bug. A bug can be defined as a discrepancy between the doc and the code. Given that I found no mention of LIBS support in distutils, I tentatively took the conservative way and judged this a new feature. However..

We found this change necessary when working on Unladen Swallow.
This may change the situation. Why was it necessary? Would other projects need it? Is it a standard in other build tools that’s an obvious oversight in distutils?

[collinwinter]

I have provided justification in the original patch submission. Without this patch, we were unable to cleanly apply gcc's feedback-directed optimization system to Python. FDO yields significant performance improvements.

[merwok]

I’m afraid performance improvements are not bug fixes, which are the only possible changes in distutils now. This change is however appreciated for packaging.