Class: Mutant::Mutator::Node::Literal::Integer::OverflowZone Private

Inherits:

Object

Object
Mutant::Mutator::Node::Literal::Integer::OverflowZone

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Defined in:: lib/mutant/mutator/node/literal/integer.rb

Overview

This class is part of a private API. You should avoid using this class if possible, as it may be removed or be changed in the future.

Integer overflow boundary probe zones.

Each entry pairs a zone boundary with a safe prime sentinel value that falls within that zone. The literal is mutated to the sentinel of the next zone above its absolute value, probing whether consuming code handles values that cross the boundary of the next integer width.

Safe primes (p = 2q + 1 where both p and q are prime) are chosen as sentinels because they cannot arise from simple arithmetic (multiplication, bit shifts, masking), providing strong guarantees against coincidental mutation kills. A mutation surviving against a safe prime is a strong signal of missing boundary validation for that integer width.

Zone layout:

Zone   Boundary  Sentinel
int8   128       167
uint8  256       467
int16  32768     55_487
uint16 65536     108_503
int32  2^31      2_667_278_543
uint32 2^32      7_980_081_959
int64  2^63      15_508_464_536_481_899_903

A literal snaps to the next zone above its absolute value. For example, a literal 100 (below int8 boundary 128) emits sentinel 167. A literal 200 (above int8, below uint8) emits sentinel 467. Values at or above 2^63 emit no sentinel as there is no higher zone to probe.

Future versions of mutant will add infrastructure to explain alive mutations, including which overflow zone a surviving sentinel belongs to and what class of bug it indicates.