Appending to executables.

[Doug Gwyn <gwyn>]

> It is not true that one cannot write a Unix executable to which
> additional functions can be appended at runtime. One of the uses of
> shared memory, available in System V and V(2), is linking executables at
> runtime. All you need to do is define the shared memory, then fork and
> exec a process that copies some of its own functions into shared memory
> and then goes to sleep.

Can we absolutely count on being able to read instruction space and
write another chunk of instruction space from a user process?

The above idea seems pretty kludgy.  Will the new memory management
system for future UNIX System V (or whatever) support a reasonable
solution to shared libraries, dynamic linking, etc.?