faulthandler: only allocate the signal handler stack when faulthandler is used

[vstinner]

BPO	37851
Nosy	@vstinner
PRs	bpo-37851: faulthandler allocates its stack on demand #15358

^{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 2019-08-21.12:41:58.560>
created_at = <Date 2019-08-14.13:44:00.117>
labels = ['library', '3.9']
title = 'faulthandler: only allocate the signal handler stack when faulthandler is used'
updated_at = <Date 2019-08-21.12:41:58.559>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2019-08-21.12:41:58.559>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2019-08-21.12:41:58.560>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2019-08-14.13:44:00.117>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 37851
keywords = ['patch']
message_count = 3.0
messages = ['349697', '350077', '350078']
nosy_count = 1.0
nosy_names = ['vstinner']
pr_nums = ['15358']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue37851'
versions = ['Python 3.9']

[vstinner]

Currently at startup, Python always call _PyFaulthandler_Init() which allocates a stack of SIGSTKSZ bytes, even if faulthandler is never used. That's a waste of memory: the stack should be allocated the first time faulthandler is used.

bpo-21131 requires to enlarge this stack size.

[vstinner]

New changeset d8c5adf by Victor Stinner in branch 'master':
bpo-37851: faulthandler allocates its stack on demand (GH-15358)
d8c5adf

[vstinner]

Note: faulthandler stack size is 16 KiB on my Fedora Linux 30 x86-64.