Self-modifying code: Difference between revisions

Revision as of 10:36, 5 September 2023

Revision as of 10:37, 5 September 2023

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Self-modifying code can be used for various purposes:

* Semi-automatic [[Program optimization (computer science)|optimizing]] of a state-dependent loop.

* Dynamic in-place code optimization for speed depending on load environment.<ref name="Caldera_1997_DOSSRC"/><ref name="Paul_1997_OD-A3"/><ref group="nb" name="NB_DR-DOS_386"/>

* [[Run time (program lifecycle phase)|Run-time]] code generation, or specialization of an algorithm in runtime or loadtime (which is popular, for example, in the ___domain of real-time graphics) such as a general sort utility&nbsp;– preparing code to perform the key comparison described in a specific invocation.

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* Evolutionary computing systems such as [[neuroevolution]], [[genetic programming]] and other [[evolutionary algorithm]]s.

* Hiding of code to prevent [[reverse engineering]] (by use of a [[disassembler]] or [[debugger]]) or to evade detection by virus/spyware scanning software and the like.

* Filling 100% of memory (in some architectures) with a rolling pattern of repeating [[opcodesopcode]]s, to erase all programs and data, or to [[burn-in]] hardware or perform [[RAM test]]s.<ref name="Wilkinson_1996"/>

* [[Executable compression|Compressing]] code to be decompressed and executed at runtime, e.g., when memory or disk space is limited.<ref name="Caldera_1997_DOSSRC"/><ref name="Paul_1997_OD-A3"/>

* Some very limited [[instruction set]]s leave no option but to use self-modifying code to perform certain functions. For example, a [[one instruction set computer]] (OISC) machine that uses only the subtract-and-branch-if-negative "instruction" cannot do an indirect copy (something like the equivalent of "*a = **b" in the [[C (programming language)|C language]]) without using self-modifying code.