Fix signed integer min/max bounds in PrimitiveType - #556
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For an n-bit two's complement integer the valid range is [-2**(n-1), 2**(n-1) - 1], but the signed branch of PrimitiveType.__init__ set max to 2**(n-1) and min to -(2**(n-1) - 1), which is one step too high on both ends (I8 reported [-127, 128] instead of [-128, 127], and likewise for the 16/32/64-bit signed types). Since validate() uses these bounds, validate(128) on I8 returned True even though encode(128) then fails in struct.pack, and validate(-128) returned False even though -128 is a legal int8. Set max to 2**(n-1) - 1 and derive min as -(max + 1). Added testSignedRange to cover the bounds, validate(), and encode/decode round-trip for each signed type. Signed-off-by: Arpit Jain <arpitjain099@gmail.com>
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I do supply-chain security work and was reading through the dtype module when the signed-integer bounds in
PrimitiveType.__init__looked off by one:For an n-bit two's complement integer the range is
[-2**(n-1), 2**(n-1) - 1], so for I8 this reports[-127, 128]instead of[-128, 127](and likewise for the 16/32/64-bit signed types).validate()uses these bounds directly, so today:validate(128)on I8 returns True, butencode(128)then fails instruct.pack(thebformat requires -128..127). validate is meant to catch that.validate(-128)on I8 returns False, even though -128 is a legal int8 that encodes fine.The fix sets max to
2**(n-1) - 1and derives min as-(max + 1). The unsigned and float branches are unchanged.I added
tests/ait/core/test_dtype.py::testSignedRange, which checks the bounds for each signed type and confirms the true min and max both validate and round-trip through encode/decode, while one past each end is rejected. Nothing in the existing dtype tests asserts these bounds, so this does not change any current expectation.pytest tests/ait/core/test_dtype.pyis green with the new test included.