ValueError for `math.atan2(0.0, 0.0)` and `cmath.phase(0.0)` using icx

Bug report

Bug description:

The math function atan2 and the cmath function phase should not raise ValueError when their arguments are zero. This is true when building CPython using an officially supported compiler such as GCC:

>>> import math
>>> import cmath
>>> math.atan2(0.0, 0.0)
0.0
>>> cmath.phase(complex(0.0, 0.0))
0.0
>>> math.atan2(0.0, -0.0)
3.141592653589793
>>> cmath.phase(complex(-0.0, 0.0))
3.141592653589793

However, The C23 standard (ISO/IEC 9899:2024) in section 7.12.4.4 for atan2 states:

A domain error may occur if both arguments are zero.

The Intel math library version 2026.0.0 sets errno to EDOM for these cases. See also PR #152825. Thus:

>>> import math
>>> import cmath
>>> math.atan2(0.0, 0.0)
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    math.atan2(0.0, 0.0)
    ~~~~~~~~~~^^^^^^^^^^
ValueError: math domain error
>>> cmath.phase(complex(0.0, 0.0))
Traceback (most recent call last):
  File "<python-input-3>", line 1, in <module>
    cmath.phase(complex(0.0, 0.0))
    ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
ValueError: math domain error
>>> math.atan2(0.0, -0.0)
Traceback (most recent call last):
  File "<python-input-4>", line 1, in <module>
    math.atan2(0.0, -0.0)
    ~~~~~~~~~~^^^^^^^^^^^
ValueError: math domain error
>>> cmath.phase(complex(-0.0, 0.0))
Traceback (most recent call last):
  File "<python-input-5>", line 1, in <module>
    cmath.phase(complex(-0.0, 0.0))
    ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
ValueError: math domain error

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-153148

この報告に対処しているように見えるため、まず PR #152825 とリンクされている PR #153148 を確認します。最初に math.atan2 と cmath.phase の CPython 実装をたどり、icx と GCC での動作を比較します。ゼロ値の引数が ValueError を発生させなくなり、文書化されている signed-zero の結果を維持すれば完了です。