Make zlib required on all platforms (simplifies code)

[gpshead]

BPO	47090
Nosy	@gpshead
PRs	gh-91246: Make zlib required instead of optional. #32043

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

Show more details

GitHub fields:

assignee = 'https://github.com/gpshead'
closed_at = None
created_at = <Date 2022-03-22.08:38:53.493>
labels = ['extension-modules', 'build', 'library', '3.11']
title = 'Make zlib required on all platforms (simplifies code)'
updated_at = <Date 2022-03-22.20:08:54.298>
user = 'https://github.com/gpshead'

bugs.python.org fields:

activity = <Date 2022-03-22.20:08:54.298>
actor = 'gregory.p.smith'
assignee = 'gregory.p.smith'
closed = False
closed_date = None
closer = None
components = ['Build', 'Extension Modules', 'Library (Lib)']
creation = <Date 2022-03-22.08:38:53.493>
creator = 'gregory.p.smith'
dependencies = []
files = []
hgrepos = []
issue_num = 47090
keywords = ['patch']
message_count = 2.0
messages = ['415750', '415809']
nosy_count = 1.0
nosy_names = ['gregory.p.smith']
pr_nums = ['32043']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue47090'
versions = ['Python 3.11']

Linked PRs

• gh-91246: Make zlib required to build python #130234
• gh-91246: Implement PEP 775: Make zlib required on platforms other than wasi  #130297

[gpshead]

We have a pile of conditionals and extra code in CPython to deal with building on systems that do not have zlib. The zlib C library has been around forever at this point and should be present on every system in the world.

zlib is already required on Windows to build CPython.

Proposal: simplify our code by removing the conditionals around zlib being optional. I'm attaching a draft PR to show what this would look like.

[gpshead]

Bringing this up on discord, others point out that the windows build requires zlib for convenience when we transitioned from having a vendored copy in our repo and that smaller "embedded" use cases may not like this if they don't already need the dep. But there have been no complaints about it on the Windows side.

binascii.crc32 was one thing that motivated me to look into "just require zlib" to get out of carrying our own suboptimal crc32 code.

looking over my PR, it can make for some awkward code with zlib right next to others that we treat as optionals. good bad or indifferent? i'm leaning towards indifferent and still enjoying fewer lines of code.