Re: Calling C from RPG: what am I doing wrong?

Hello,

This was a few years back and only to do with return values, large
varchars as parameters were fine. I think the storage overflow problem
only arose when large return values(65K) were assigned to many different
variables ( the context was in mapping the elements of an xml document
to rpg variables ).

There can be, at most 16776704 bytes (approx 16mb) of automatic storage. Sounds like you were doing something that caused it to exceed the number of bytes of automatic storage.

Do you remember if it was MCH4429 or MCH4216 or something else?

If you want to see what I mean, try something like this:

H DFTACTGRP(*NO)

D proc1 pr 10i 0

c callp proc1
c eval *inlr = *on

P proc1 b
D proc1 pi 10i 0
D foo s 65535a dim(200)
D foo2 s 65535a dim(56)
c return 0
P E

On my system, the above program won't even compile.. the compiler logs errors and ends :) But, if I change the value of the 2nd dim to 55, it compiles and runs without error, because the size of the automatic storage it's using is less than 16776704

By contrast, try this:

H DFTACTGRP(*NO)

D proc1 pr 10i 0
D proc2 pr 65535a

c callp proc1
c eval *inlr = *on

P proc1 b
D proc1 pi 10i 0
D foo s 65535a dim(254)
c eval foo(1) = proc2()
c return 0
P E

P proc2 b
D proc2 pi 65535a
c return *all'x'
P E

Even though my DIM() is 254 (less than 255!) the compile fails it has exceeded automatic storage limits. that's because the return value from proc2() requires an additional 65535 of automatic storage... indeed, I think it uses it not once, but more than once, since I have to cut my DIM back to 252 for this version to work...