[3.15] gh-156933: Widen narrow integer results in ctypes callbacks (GH-157045) - #158295
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…ythonGH-157045) _CallPythonObject() only wrote restype->size bytes into the closure's result buffer, leaving the unused high-order bits of the ffi_arg-sized register untouched. libffi's ffi_prep_closure_loc() documents that integral types narrower than a machine register must be widened to fill it, sign-extending signed types. On architectures that always read the full register for narrow return values (s390x), this leaves garbage in the high bits, which broke libclang callbacks used by cindex.py. (cherry picked from commit b6f9a50) Co-authored-by: Lazizbek Ergashev <lazerg2@gmail.com>
ZeroIntensity
approved these changes
Sep 27, 2026
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Oh, wait a minute, this is going to fail because 3.15 doesn't have the utility we're using in the tests. I'll fix that. |
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Should be fixed now. |
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_CallPythonObject() only wrote restype->size bytes into the closure's result buffer, leaving the unused high-order bits of the ffi_arg-sized register untouched. libffi's ffi_prep_closure_loc() documents that integral types narrower than a machine register must be widened to fill it, sign-extending signed types. On architectures that always read the full register for narrow return values (s390x), this leaves garbage in the high bits, which broke libclang callbacks used by cindex.py.
(cherry picked from commit b6f9a50)
Co-authored-by: Lazizbek Ergashev lazerg2@gmail.com