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gh-153144: Avoid checking errno for atan2 #153148

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gh-153144: Avoid checking errno for atan2 #153148

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503fd4a
gh-153144: Avoid checking `errno` for `atan2`
hpkfft Jul 5, 2026
c9c51ad
gh-153144: Added NEWS entry
hpkfft Jul 20, 2026
287e6ee
gh-153144: Modify comments as requested in review
hpkfft Jul 21, 2026
cbe759a
Merge branch 'main' into atan2
hpkfft Aug 1, 2026
91257f2
Merge branch 'main' into atan2
hpkfft Aug 13, 2026
25ec8e2
Add comments as requested in review
hpkfft Aug 14, 2026
43f7398
Revert gh-146402 and update NEWS entry
hpkfft Aug 14, 2026
5b6d005
Merge branch 'main' into atan2
skirpichev Aug 30, 2026
ead2720
Make NEWS entry a little shorter.
hpkfft Aug 30, 2026
d546e81
The copysign function does not need to check errno.
hpkfft Aug 30, 2026
f4ed052
Merge branch 'main' into atan2
hpkfft Sep 8, 2026
82448e1
Add cmath tests and update NEWS entry
hpkfft Sep 8, 2026
288fb8b
Merge branch 'main' into atan2
hpkfft Sep 18, 2026
be0ed87
Expand comments to explain why we ignore errno
hpkfft Sep 18, 2026
b991892
Merge branch 'main' into atan2
hpkfft Sep 18, 2026
72842e1
Merge branch 'main' into atan2
hpkfft Oct 1, 2026
11c56c4
Merge branch 'main' into atan2
hpkfft Oct 3, 2026
6a92490
Change as requested in review
hpkfft Oct 3, 2026
6a48f02
Merge branch 'main' into atan2
hpkfft Oct 4, 2026
8594452
Add tests for math.atan2() and update NEWS
hpkfft Oct 4, 2026
527afd1
Remove decorative `*` from comment in cmathmodule
hpkfft Oct 4, 2026
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Expand comments to explain why we ignore errno
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@hpkfft
hpkfft committed Sep 18, 2026
commit be0ed872f22216dd8bf99ed76071302e215953d8
6 changes: 4 additions & 2 deletions Modules/cmathmodule.c
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Expand Up @@ -1004,8 +1004,10 @@ cmath_phase_impl(PyObject *module, Py_complex z)
{
double phi;

phi = atan2(z.imag, z.real); /* should not cause any exception */
/* gh-153144: Ignore atan2() errno on purpose. */
phi = atan2(z.imag, z.real);
/* gh-153144: Ignore atan2() errno on purpose since it can optionally be
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picnixz marked this conversation as resolved.
* EDOM, which we should ignore, or ERANGE if phi underflows,
* which is silent on Python. Overflow is not possible. */
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skirpichev marked this conversation as resolved.
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return PyFloat_FromDouble(phi);
}

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7 changes: 5 additions & 2 deletions Modules/mathmodule.c
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Expand Up @@ -1149,11 +1149,14 @@ FUNC1(atan, atan, 0,
"atan($module, x, /)\n--\n\n"
"Return the arc tangent (measured in radians) of x.\n\n"
"The result is between -pi/2 and pi/2.")
FUNC2NE(atan2, atan2, // gh-153144: Ignore atan2() errno on purpose.
/* gh-153144: Ignore atan2 and atan2pi errno on purpose since it can optionally
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hpkfft marked this conversation as resolved.
* be EDOM, which we should ignore, or ERANGE on underflow, which is
* silent on Python. Overflow is not possible. */
Comment on lines +1154 to +1156

@skirpichev skirpichev Oct 4, 2026

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Suggested change
/* gh-153144: Ignore atan2 and atan2pi errno on purpose since it can optionally
* be EDOM, which we should ignore, or ERANGE on underflow, which is
* silent on Python. Overflow is not possible. */

@hpkfft hpkfft Oct 4, 2026

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@vstinner asked for the "ignore errno on purpose" part of this comment on August 14: #153148 (comment)
@picnixz asked to "document the reason why we ignore errno in this case" on September 18: #153148 (comment)

FUNC2NE(atan2, atan2,
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hpkfft marked this conversation as resolved.
"atan2($module, y, x, /)\n--\n\n"
"Return the arc tangent (measured in radians) of y/x.\n\n"
"Unlike atan(y/x), the signs of both x and y are considered.")
FUNC2NE(atan2pi, m_atan2pi, // gh-153144: Ignore atan2pi() errno on purpose.
FUNC2NE(atan2pi, m_atan2pi,
"atan2pi($module, y, x, /)\n--\n\n"
"Return the arc tangent (measured in half-turns) of y/x.\n\n"
"Unlike atanpi(y/x), the signs of both x and y are considered.")
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