Excessive stack usage for clang-cl debug builds on Windows

[chris-eibl]

test.test_call.TestRecursion.test_margin_is_sufficient fails on the AMD64 Windows Server 2025 Clang 3.14 buildbot.

The table lists safe_margin before it is multiplied, because 3.14 and main use different extra percents

cpython/Lib/test/test_call.py

Lines 1105 to 1107 in 5b34363

	# Add an (arbitrary) extra 25% for safety
	safe_margin = safe_margin * 5 / 4
	self.assertLess(safe_margin, _testinternalcapi.get_stack_margin())

and _testinternalcapi.get_stack_margin(), which is actually just _PyOS_STACK_MARGIN_BYTES.

branch	compiler	build	safe_margin	_PyOS_STACK_MARGIN_BYTES
main	MSC v.1951	debug	20080	32768
main	clang-cl 22.1.3	debug	26032	32768
main	clang-cl 22.1.3	release	1200	16384
3.14	MSC v.1944	debug	23168	32768
3.14	clang-cl 22.1.3	debug	33920	32768
3.14	clang-cl 22.1.3	release	992	16384
3.14	clang-cl 22.1.3	debug with -Og	1536	32768

Using -Og drastically improves stack usage.

Linked PRs

• gh-157789: Use compiler option -Og in case of clang-cl debug builds #157791