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Hello David,

I have a question regarding the following code:

D MyDS DS LIKEDS ( gMyOtherDS ) DIM ( 100 )
D BASED ( MyPtr )
D MyPtr S *

My question: Why did you use the BASED keyword? Why bother using BASED and then %ALLOC? Why not just do this?

D MyDS DS LIKEDS ( gMyOtherDS ) DIM ( 100 )
D MyPtr S *

MyPtr = %addr(MyDS);
PGM2(MyPtr);

Why tell the OS to let you handle the allocation if you're just going to allocate the exact size of the structure?



David FOXWELL wrote:
Hi,

I just wrote my first program ever that passed a pointer from one program to another. I used it to access a data structure in the calling program that was alimented by the program being called. I won't explain why I did not just pass the data structure as a parameter. Anyway, it seems to work. I was a little surprised and found it good fun. However, having rather stumbled upon the solution when it didn't work, I ask the experts out there for confirmation :



Code simplified.
D PGM2 PR EXTPGM ( 'PGM2' )
D OutParm *


D MyDS DS LIKEDS ( gMyOtherDS ) DIM ( 100 )
D BASED ( MyPtr )
D MyPtr S *

/free

PGM2 ( MyPtr );

/end-free



This crashed because I understand I need to allocate storage for MyPtr before the call.

So I inserted this and it worked :
wLen = %LEN ( wMrsAdh ( 1 ));
MyPtr = %ALLOC ( wLen * 100 );

Is this the right way to initialize the pointer?

Thanks.


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