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| author | Steve Dower <steve.dower@python.org> | 2021-12-09 18:31:54 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2021-12-09 18:31:54 (GMT) |
| commit | 3363e1cb05d0d19ed172ea63606d8cb6268747fc (patch) | |
| tree | 4a387cf8f7cc9b6822607b3b4856e097ad892908 | |
| parent | 44b0e76f2a80c9a78242b7542b8b1218d244af07 (diff) | |
| download | cpython-3363e1cb05d0d19ed172ea63606d8cb6268747fc.zip cpython-3363e1cb05d0d19ed172ea63606d8cb6268747fc.tar.gz cpython-3363e1cb05d0d19ed172ea63606d8cb6268747fc.tar.bz2 | |
bpo-46018: Ensure that math.expm1 does not raise on underflow (GH-29997)
| -rw-r--r-- | Misc/NEWS.d/next/Library/2021-12-09-00-44-42.bpo-46018.hkTI7v.rst | 1 | ||||
| -rw-r--r-- | Modules/mathmodule.c | 8 |
2 files changed, 7 insertions, 2 deletions
diff --git a/Misc/NEWS.d/next/Library/2021-12-09-00-44-42.bpo-46018.hkTI7v.rst b/Misc/NEWS.d/next/Library/2021-12-09-00-44-42.bpo-46018.hkTI7v.rst new file mode 100644 index 0000000..6ff76f5 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2021-12-09-00-44-42.bpo-46018.hkTI7v.rst @@ -0,0 +1 @@ +Ensure that :func:`math.expm1` does not raise on underflow. diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c index 84b5b95..011ce0a 100644 --- a/Modules/mathmodule.c +++ b/Modules/mathmodule.c @@ -985,9 +985,13 @@ is_error(double x) * On some platforms (Ubuntu/ia64) it seems that errno can be * set to ERANGE for subnormal results that do *not* underflow * to zero. So to be safe, we'll ignore ERANGE whenever the - * function result is less than one in absolute value. + * function result is less than 1.5 in absolute value. + * + * bpo-46018: Changed to 1.5 to ensure underflows in expm1() + * are correctly detected, since the function may underflow + * toward -1.0 rather than 0.0. */ - if (fabs(x) < 1.0) + if (fabs(x) < 1.5) result = 0; else PyErr_SetString(PyExc_OverflowError, |