17 Sep
2015
17 Sep
'15
6:13 p.m.
On Sep 17, 2015, at 5:42 PM, dwight <dkelvey at
hotmail.com> wrote:
I am quite aware of the caching problem.
What I don't understand is what problem they thought they
were fixing by outlawing self modifying code.
Self modifying code in sense #4 from my earlier note (i.e., a program that scribbles on
bits of itself) is a perfectly fine programming technique if you have an ISA that leaves
you no choice, and a good choice in some other specialized cases. Boot time customization
of critical kernel paths is an example.
The issue is that such code is hard to maintain because the source does not directly
reflect what is executed. So even by the standards of assembly language programming,
self-modifying code adds a level of pain. If it's poorly documented, you're in
real trouble.
For a nice example, read "Mel, the story of a Real Programmer". :-)
paul