Remove the concept of platform-specific directories

[zware]

BPO	28046
Nosy	@doko42, @vstinner, @ned-deily, @xdegaye, @zware, @moreati, @yan12125
PRs	bpo-28046: Remove MACHDEPPATH from Modules/Setup.dist #5289
Files	remove_plat.diff get_sysconfigdata_name.diff sysconfigdata_env_var.diff sysconfigdata_ABIFLAGS.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 = None
closed_at = <Date 2018-01-24.16:20:41.981>
created_at = <Date 2016-09-09.17:58:33.545>
labels = ['type-feature', '3.7', 'build']
title = 'Remove the concept of platform-specific directories'
updated_at = <Date 2018-01-24.16:20:41.980>
user = 'https://github.com/zware'

bugs.python.org fields:

activity = <Date 2018-01-24.16:20:41.980>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2018-01-24.16:20:41.981>
closer = 'vstinner'
components = ['Build', 'Cross-Build']
creation = <Date 2016-09-09.17:58:33.545>
creator = 'zach.ware'
dependencies = []
files = ['44506', '44530', '44532', '45232']
hgrepos = []
issue_num = 28046
keywords = ['patch']
message_count = 35.0
messages = ['275360', '275363', '275427', '275429', '275430', '275433', '275436', '275438', '275442', '275475', '275477', '275518', '275519', '275532', '275592', '275599', '275635', '275638', '275642', '275643', '275650', '275664', '275667', '275677', '275711', '275845', '275846', '275850', '276245', '279508', '279592', '303426', '310539', '310605', '310608']
nosy_count = 8.0
nosy_names = ['doko', 'vstinner', 'ned.deily', 'xdegaye', 'python-dev', 'zach.ware', 'Alex.Willmer', 'yan12125']
pr_nums = ['5289']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue28046'
versions = ['Python 3.6', 'Python 3.7']

[zware]

As a follow-on to bpo-28027, the attached patch removes the concept of platform-specific directories (Lib/plat-darwin, Lib/plat-x86_64-linux-gnu, etc). I believe this should be fine for cross-builds (at least as fine as the previous solution for _sysconfigdata), but I'd like someone to test it for me since I have no experience with cross-builds.

[vstinner]

You might also remove Lib/_sysconfigdata.py from .gitignore.

[doko42]

not sure if I fully understand:

• The patch encodes the multiarch triplet into the _sysconfigdata
  name and installs it into the standard lib dir.
• It removes the PLATDIR macro
• what happens to the constants modules which are currently
  found in the platdir? These vary across architectures and
  should not be install in the standard lib dir.

[zware]

Those were removed in bpo-28027, by BDFL decree.

[doko42]

this comes as a surprise. I can't remember that discussion and decision.

[zware]

Sorry, it happened at the sprint at Instagram. Do you have a use for those modules that we need to reconsider?

[vstinner]

this comes as a surprise. I can't remember that discussion and decision.

Removing these modules is not a new idea: I just posted a message to the issue bpo-28027 to complete the history of this change.

[doko42]

The removal is not following the guidelines to first deprecate these for a release, and then to remove them. I know that at least the RTLD_* constants are used in a number of places, which will just stop working.

I'm not against removing these in 3.7, however they should be deprecated in 3.6 first. There is no harm done with this approach.

[vstinner]

Matthias Klose added the comment:

The removal is not following the guidelines to first deprecate these for a release, and then to remove them. I know that at least the RTLD_* constants are used in a number of places, which will just stop working.

Please continue the discussion in the issue bpo-28027, reopen it if you want.

[zware]

Xavier: Could you please make sure this doesn't break anything for Android/cross-builds?

[xdegaye]

Sure, I was already planning to do it :)