RE: pointer problem

I apologise for the original post, which was sent while trying to complete a test procedure before quittin' time on a Friday afternoon. Most of my brain cells had already gone home for the weekend.

I was indeed trying to pass a template DS to another procedure without initialising it. I should have had my own DS that was defined on the template, which I forgot. I realised my mistake at breakfast on Saturday morning and wasn't looking forward to reading the replies to my post today. I was expecting to get a real pasting. However, everyone was very kind and I thank them all.

I still found the thread quite interesting and maybe it will have served someone else too.

-----Message d'origine-----
De : rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] De la part de Larry Ducie
Envoyé : samedi 1 août 2009 01:25
À : RPG400
Objet : Re: pointer problem


Hi David,

I agree with Scott on this one.

For example, the DS may simply be a template designed to
NEVER have memory allocated to it and you may be expected to
create your own DS likeDS the original DS. Allocating memory
to the original DS and using it could be disasterous, or at
the very least useless.

Alternatively, the pointer may need to be passed to an API.
In this case allocating memory to the basing pointer would be
required. But how much memory should you allocate? The amount
of memory to allocate may be determined by other API calls
and can not be deduced a priori, or it may be obvious from
the API docs and constant.

A further option is that there is a second pointer which is
allocated the total memory required and the basing pointer
you have your DS based on is simply used to overlay the DS
over the original pointer data at specified offsets. The data
could be allocated sirectly using the %alloc BIF or could be
inside a User Space - as in many list API results.

The point is, the solution is in your application code and
can not be provided by glib answers from us based on one or
two lines of sample code. You need to know what it is you are
trying to do with this based DS in order have a complete
picture of the process involved. Once you have this
knowledge, however, you will probably not need any of us to
help you. You will now know whether you should be allocating
memory to the pointer or creating a copy DS and using that instead.

Catch 22.

Not helpful, but the best I can offer, other than
generalisations and lists of possible solutions. If you are
using pointers, it is not the time to experiment with
possibilities - you need to know exactly what you are doing.

Cheers

Larry Ducie



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