Re: Memory Leaks in RPG (was: Is RPG 'DEAD")

yep 2 programs retrieving the pointer to the same user space will see the
same memory address! why? because the object in question is in the same
place regardless of the process trying to access it.

Thanks,
Tommy Holden



From:
David Gibbs <david@xxxxxxxxxxxx>
To:
RPG programming on the AS400 / iSeries <rpg400-l@xxxxxxxxxxxx>
Date:
06/19/2008 06:17 AM
Subject:
Re: Memory Leaks in RPG (was: Is RPG 'DEAD")



Scott Klement wrote:

It's theoretically possible to put a pointer in a user space and share
it with another job, but doing so is dangerous for this very reason...
if the job that allocated the memory ends, the pointer will point to
unreserved memory, and produce the same sorts of "unpredictable results"

that you'd have with a buffer overflow.

Even if you handed a pointer around from job to job, would different
jobs even be able to access the same memory? Seems to me that the OS
should protect against memory access across job domains (unless the
memory is allocated in an approved 'shared memory' method).

I'm not at a system right now ... but I'm wondering if, when you
retrieve a pointer to the same user space in two different jobs, you get
the same pointer value?

b) Or, use the shared memory APIs (shmget, shmat, shmdt, etc) to reserve

shared memory.

Hmmm ... this makes me wonder if the shared memory api's use user spaces
under the covers?

Weird as this sounds ... even though I was annoyed at the impetus of
this thread, it's gotten darn interesting.

david