Undefined behavior due to incorrect usage of %p in format strings

[ZackerySpytz]

BPO	36594
Nosy	@brettcannon, @mdickinson, @skrah, @serhiy-storchaka, @ZackerySpytz
PRs	bpo-36594: Fix incorrect use of %p in format strings #12769

^{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 2019-05-14.03:55:31.826>
created_at = <Date 2019-04-11.00:10:57.376>
labels = ['extension-modules', 'interpreter-core', '3.7', '3.8']
title = 'Undefined behavior due to incorrect usage of %p in format strings'
updated_at = <Date 2019-05-14.03:55:31.825>
user = 'https://github.com/ZackerySpytz'

bugs.python.org fields:

activity = <Date 2019-05-14.03:55:31.825>
actor = 'brett.cannon'
assignee = 'none'
closed = True
closed_date = <Date 2019-05-14.03:55:31.826>
closer = 'brett.cannon'
components = ['Extension Modules', 'Interpreter Core']
creation = <Date 2019-04-11.00:10:57.376>
creator = 'ZackerySpytz'
dependencies = []
files = []
hgrepos = []
issue_num = 36594
keywords = ['patch']
message_count = 4.0
messages = ['339907', '340151', '340152', '341564']
nosy_count = 5.0
nosy_names = ['brett.cannon', 'mark.dickinson', 'skrah', 'serhiy.storchaka', 'ZackerySpytz']
pr_nums = ['12769']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue36594'
versions = ['Python 2.7', 'Python 3.7', 'Python 3.8']

[ZackerySpytz]

The attached PR fixes incorrect usages of %p in format strings.

[serhiy-storchaka]

Are not all pointer types (except pointers to functions) automatically converted to/from void*.

[skrah]

gcc warns with -pedantic:

ptr.c: In function ‘main’:
ptr.c:5:13: warning: format ‘%p’ expects argument of type ‘void *’, but argument 2 has type ‘int *’ [-Wformat=]
printf ("%p", &i);

It is pedantic indeed, I wonder if machines with different pointer sizes still exist.

[brettcannon]

New changeset 1a2252e by Brett Cannon (Zackery Spytz) in branch 'master':
bpo-36594: Fix incorrect use of %p in format strings (GH-12769)
1a2252e