Lit. Buffer overruns 1723

although there are machine instructions that require explicit length bounds before the instruction starts ... so there are some instruction semantics that require that both origin and destination lengths are explicitly known as part of invoking the instruction (as part of the instruction semantics). this tends to promote infrastructures with determinable storage area lengths as part of invoking the instruction ... as compared to infrastructures where lengths are actually explicit ... like strings where the boundaries are actual length paradigms but implicit in data structures embedded in the storage areas.

one of the things normally required for most ABC implementations are infrastructure determinable storage lengths that can be used as part of bounds specification. for instance the prevalent string paradigm doesn't have a length value for an ABC operation that is able to determine whether an arbitrary byte location is on one side of the string bound or the other side of the string bound ... without scanning the string itself for the data-pattern bound characteristic.

Most ABC operations tend to have calculatable storage address bound based on a infrastructure providing either explicit start-length or start-end value pairs .... as opposed to infrastructure bounds semantics based on arbitrary data pattern contained somewhere in the storage area (or no available infrstructure determinal bound pair value at all).

in the 370 MVCL instruction both the source and target origins and lengths are specified separately (along with optional fill character to be used in situation where the source length is less than the target length). This would be considered a ABC semantics that is part of the machine instruction specification.

One possible difference between most higher level programming languages and most machine programming languages ... is that in the higher level programming languages, the actual machine instructions don't tend to be known by the programmer ... and there can be different instructions generated-executed with ABC active or not active. However, other ABC paradigms are possible ... like with the 370 MVCL instruction where the bounds specification are actually part of the instruction semantics. Other ABC paradigms are at a more gross level ... the use of store protect (and virtual address space mapping) to preclude programs from wild stores outside their security domain (common countermeasure preventing arbitrary applications from overlaying kernel storage areas).

Now, many hardware architectures have had various kinds of storage protection mechanisms for decades ... which doesn't correct program behavior any more than fine-grain ABC operations correct program behavior. However, it has become recognized that various kinds of application mis-behavior countermeasures are an extremely useful characteristic.

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