Self Modifing Code was RE: Harvard vs. vonNeuman

>> It is interesting that different people have different >> ideas as to what self modifying code is. Actually, the >> ability to load code and execute from a mass storage is >> self modifying.

>> Code that uses a variable value for a table to look up >> execution addresses is self modifying.

>> Most every >> multitasking system I've seen are self modifying.

>> I think what people consider dangerous self modifying is >> when the program alters the actual execution instructions >> in memory and then executes them. It is strange that this >> form gets such a large amount of emotional negative >> response while other types are hardly considered issues. >> No matter how the code is written, one can make bad code >> in most any form. One can also make good code as well. >> There is no reason why self modifying code should be any >> more dangerous than any other type of coding if done with a >> complete understanding of what the limitations are. What is >> the difference between replacing one or two instructions >> and then executing them or replacing an overlay and then >> executing that overlay? Other than size, both are doing the >> same thing. One is forbidden while the other is normal operation.