Static, Automatic and Heap Storage

Hi all,

The discussion about service programs has left me getting a bit confused
about the different types of storage.

I thought that one of the differences between static and automatic storage
is that one of them (static ?) contains data which has the same storage
requirements for every call of the program - for example if sflsiz=sflpag
the subfile fields are all kept in static(?) storage, whereas for extending
subfiles automatic(?) storage will be used.  Am I understanding this
correctly ? Is one of the types of storage actually linked to the program
object itself in some way ?

Is heap storage only applicable where you are using the alloc and dealloc
commands and doing things with pointers ? How does it differ from the
automatic storage as described above ?

Does the term "scoped to activation group" mean shared within one
activation group ?  Is it possible to share one area of storage between
different activation groups ?  (Intentionally ! <g>)

- thinking about the last point, I imagine by using pointers you would
achieve this ?  I guess even passing parameters has the same end result
that storage is shared, whether activation groups are the same or
different.

Thanks In Advance for answers.

Nigel.


    Alexei Pytel wrote...
>Static storage is scoped to activation group, so if programs from
different
>activation groups are calling modules in a service program, running in a
>named activation group, they should expect to see changes to static
>variables, made in previous calls, even coming from unrelated activation
>groups.
>
>Automatic (local) storage is allocated in stack and is not affected by
>activation group.
>
>Heap storage is also scoped to activation group, so all dynamic
allocations
>made from service program modules will go to the same heap (which will be
>freed when this activation group ends).
>This may lead to orphan pointers in other activation groups.

>Basically, there is no problem in using named activation group for service
>program if you understand what you are doing.



+---
| This is the RPG/400 Mailing List!
| To submit a new message, send your mail to RPG400-L@midrange.com.
| To subscribe to this list send email to RPG400-L-SUB@midrange.com.
| To unsubscribe from this list send email to RPG400-L-UNSUB@midrange.com.
| Questions should be directed to the list owner/operator: david@midrange.com
+---