RE: Memory Allocation Question -- RPG400-L

If you're storing your pointer in a data-structure, are you using Overlay to
define subfields?  Automatic alignment of subfields doesn't work when using
Overlay.  Pointers must align to 16 byte boundary.

Eric DeLong
Sally Beauty Company
MIS-Project Manager (BSG)
940-898-7863 or ext. 1863



-----Original Message-----
From: Smith, Nelson [mailto:NSmith@lincare.com]
Sent: Friday, January 03, 2003 9:55 AM
To: 'rpg400-l@midrange.com'
Subject: RE: Memory Allocation Question


In my debugging, I've eliminated all references to the pointer except on the
alloc and dealloc statements, so it must be something else I am doing to
other variables that have an effect on it.

The only oddity I notice (and it may just be a quirk of debug) is that the
data structure contains an array of 400 elements, 46 bytes each, and no
matter if I allocate 46 bytes to the pointer or 46*400, I see the entire 400
elements when I do F11 on the ds name.  I'm trying to only use the amount of
memory needed rather than the maximum 400 array elements.  Does Strdbg show
all 400 even if you did not allocate that many?  When I only allocate enough
memory for one array element, some of the area debug is showing me past that
first element is getting into a second ds that is allocated and reallocated.
Could this cause some corruption to the first pointer?  Is that what you
mean by "touching" the pointer?  Is there any way to see the tag bit in
debug?

> -----Original Message-----
> From: Jon Paris [SMTP:Jon.Paris@Partner400.com]
> Sent: Friday, January 03, 2003 10:23 AM
> To:   rpg400-l@midrange.com
> Subject:      Memory Allocation Question
>
>  >> If the value of the pointer at deallocate time is still the same as
> what
> was returned from the initial allocate, what else about it can be
> corrupted?
>
> 1) Have you moved (or in any way "touched" the pointer in such a way as it
> could have been invalidated?  The content would appear the same but the
> tag
> bit would have been turned off rendering it useless as a pointer.
>
> 2) Did you do a realloc and fail to store the new pointer (i.e are you
> attempting to free using the original pointer when the realloc may have
> changed it?
>
> Jon Paris
> Partner400
>
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