QUERY · ISSUE

Overflow converting -2147483648 to int when using MPZ

openby markstzopened 2020-08-12updated 2020-08-12

py-core

When MICROPY_LONGINT_IMPL == MICROPY_LONGINT_IMPL_MPZ, calling mp_obj_get_int() for a Python variable that contains the value -2147483648 results in an overflow converting long int to machine word error.

If MICROPY_LONGINT_IMPL == MICROPY_LONGINT_IMPL_LONGLONG instead, the conversion works OK.

Is the MPZ overflow check incorrect?

CANDIDATE · ISSUE

Converting minimum long long value to string results in incorrect output

closedby doogleopened 2015-01-13updated 2017-04-11

When mp is configured to use 'long long' ints (MICROPY_LONGINT_IMPL == MICROPY_LONGINT_IMPL_LONGLONG), the following code:

print(-0x7fffffffffffffff-1)

results in the string:

-'..--).0-*(+,))+(0(

rather than:

-9223372036854775808

This is due to mp_obj_int_formatted() trying to negate the number, which fails in this case. The subsequent conversion to a string then results in invalid characters due to (I think) signedness issues.

Assessment

Q Qwen · high

Both issues concern integer overflow handling in MicroPython's integer implementation, specifically involving the minimum representable value and two's complement behavior. However, they address different problems: Issue #6332 is about mp_obj_get_int() failing with MPZ implementation when converting -2147483648, while Issue #1064 is about mp_obj_int_formatted() producing corrupted output with LONGLONG implementation when printing -9223372036854775808. They share the same root cause concept (overflow at minimum value) but affect different code paths (get_int vs formatted output) and different implementations (MPZ vs LONGLONG). Neither resolves the other's specific problem.

Suggested action

Keep both issues open as they address distinct bugs. Consider cross-referencing them in comments since they may share a common fix strategy for handling minimum value overflow in two's complement arithmetic.

Overflow converting -2147483648 to int when using MPZ

Converting minimum long long value to string results in incorrect output

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