Testing math_testcases.txt lacks support for signed zeros

[skirpichev]

Feature or enhancement

Proposal:

This file tested, using result_check() helper:

cpython/Lib/test/test_math.py

Line 175 in beee91c

def result_check(expected, got, ulp_tol=5, abs_tol=0.0):

which lacks checking of zero sign (while some entries in the data file - have signed zeros). C.f. cmath_testcases.txt, which tested with rAssertAlmostEqual(), that has such special case:

cpython/Lib/test/test_cmath.py

Lines 124 to 131 in beee91c

	# if both a and b are zero, check whether they have the same sign
	# (in theory there are examples where it would be legitimate for a
	# and b to have opposite signs; in practice these hardly ever
	# occur).
	if not a and not b:
	if math.copysign(1., a) != math.copysign(1., b):
	self.fail(msg or 'zero has wrong sign: expected {!r}, '
	'got {!r}'.format(a, b))

I think that first helper should be adjusted to do same. I'll work on a patch.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-123836: check zero signs in math_testcases.txt #123854
• [3.13] gh-123836: Check zero signs in math_testcases.txt (GH-123854) #124161
• [3.12] gh-123836: Check zero signs in math_testcases.txt (GH-123854) #124162
• gh-123836: workaround fmod(x, y) bug on Windows #124171
• [3.12] gh-123836: workaround fmod(x, y) bug on Windows (GH-124171) #124186
• [3.13] gh-123836: workaround fmod(x, y) bug on Windows (GH-124171) #124187

[skirpichev]

PR is ready for review: #123854

[vstinner]

Implemented as 28aea5d. Backports will follow.

[encukou]

This broke the Windows 10 buildbot: #123854 (comment)