Mac Forum / Programming / Mac Programming / November 2005

It would execute the data,
which was the point if one were writing self modifying code.

Some memories are not sweet.

Let's focus on the novelty of inheritance and forget calculated offset
branch arrays.

That depends *ENTIRELY* on the processor type (and sometimes on the
individual processor chip) involved...

An "unenhanced" Apple IIe with a 6502 processor is a prime example, even
though it isn't a mainframe like the thread originally started with -
Some 6502s would hit certain "enhanced" (65C02) instructions, and
depending on whether it was a western digital chip or somebody else's,
might execute a useful (but only to be counted on when running on *THAT
SPECIFIC CHIP*) function that you had to figure out the details of for
yourself if you were crazy enough to try to actually *USE* it, while the
next one would hit the same instruction and send the machine into a hard
lockup, another would spew a string of random bits all through memory,
and yet another one would treat that instruction exactly the same as a
NOP, leaving you without any idea that it had ever encountered a "bad"
instruction.

Self-modifying code *ON PURPOSE* is one thing... Bungled pointer math
turning the guts of your code into an array of credit card numbers,
addresses, or similar "not really program", is a nightmare.