new file mode 100644
@@ -0,0 +1,46 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Khem Raj <khem.raj@oss.qualcomm.com>
+Date: Sat, 12 Sep 2026 00:00:00 -0700
+Subject: [PATCH] parser: avoid undefined double to long conversion in
+ float_as_int_without_noise
+
+float_as_int_without_noise() returns early when the floored value fits
+in a long:
+
+ if (floor_val == static_cast<long>(floor_val))
+
+For values outside the range of long (e.g. 3.453e21) the conversion is
+undefined behavior. clang (-O2) takes advantage of that and folds the
+round trip into "floor_val is integral", which is always true, so the
+denoising is skipped and try_real(3.453e21, denoise=True) returns
+3452999999999999737856 instead of 3453000000000000000000:
+
+ tests/test_fastnumbers_examples.py::test_try_real FAILED
+ tests/test_fastnumbers_examples.py::test_try_forceint FAILED
+
+Only do the conversion when the value is within the range of long.
+
+Upstream-Status: Pending
+Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
+---
+ src/cpp/parser.cpp | 8 +++++++-
+ 1 file changed, 7 insertions(+), 1 deletion(-)
+
+--- a/src/cpp/parser.cpp
++++ b/src/cpp/parser.cpp
+@@ -92,8 +92,14 @@
+
+ // If the given float can fit a C long without loss then no need
+ // to go through the below rounding steps.
++ // Converting a double that is outside the range of long is undefined
++ // behavior, and clang uses that to fold this check into "floor_val is
++ // integral", which is always true and skips the denoising below for large
++ // values. Make sure the value is in range before converting.
+ const double floor_val = std::floor(val);
+- if (floor_val == static_cast<long>(floor_val)) {
++ constexpr double long_limit = -static_cast<double>(std::numeric_limits<long>::min());
++ if (floor_val >= -long_limit && floor_val < long_limit
++ && floor_val == static_cast<long>(floor_val)) {
+ return val_int;
+ }
+
@@ -4,6 +4,7 @@ LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://LICENSE;md5=d32431d1b650010945da4e078011c8fa"
+SRC_URI += "file://0001-parser-avoid-undefined-double-to-long-conversion-in-.patch"
SRC_URI[sha256sum] = "07266a2fca9e08eeb5a6c70be4c8db3637db9b930ea5198facbbb9b0b31d4d03"
inherit pypi python_setuptools_build_meta ptest-python-pytest
float_as_int_without_noise() returns early when the floored value fits in a long, checking it with floor_val == static_cast<long>(floor_val). For values outside the range of long the conversion is undefined behavior; clang -O2 folds the round trip into "floor_val is integral", which is always true, so the denoising is skipped: FAIL: tests/test_fastnumbers_examples.py:test_try_real FAIL: tests/test_fastnumbers_examples.py:test_try_forceint assert 3452999999999999737856 == 3453000000000000000000 Add a patch that only does the conversion when the value is in range. A reduced reproducer returns the wrong answer with the recipe's clang++ at -O2 and the right one with the fix (and with -O0 or gcc). AI-Generated: Uses Claude Code Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com> --- ...efined-double-to-long-conversion-in-.patch | 46 +++++++++++++++++++ .../python/python3-fastnumbers_5.2.0.bb | 1 + 2 files changed, 47 insertions(+) create mode 100644 meta-python/recipes-devtools/python/python3-fastnumbers/0001-parser-avoid-undefined-double-to-long-conversion-in-.patch