RE: Safe to maintain pointer to errno() ?

Dennis;

Here are two errNo procedures I use regularly. You could probably compile the errNo procedure right out of the box, errNoTrap uses several messaging functions, which I can attach if you are interested, or you can modify it any way you wish.

One note, although the errNo procedure allows you to assign a value to the errNo memory, but it is not recommended to do so, generally.

These are the prototypes that are contained in the SVS9998 include.
D errNo PR 10I 0
D 10I 0 Const Options(*NOPASS)

D errNoTrap PR 10I 0
D 10I 0 Const Error Number
D 100A Const Varying Function Name
D 10A Const Options(*NOPASS) Message Type
D 256A Const Varying Options(*NOPASS) Call Stack Entry


errno()
http://code.midrange.com/008d29b820.html

errNoTrap()
http://code.midrange.com/f97f8f9e12.html

Duane Christen

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Duane Christen
Senior Software Engineer
(319) 790-7162
Duane.Christen@xxxxxxxxxx

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-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Dennis Lovelady
Sent: Wednesday, October 13, 2010 11:37 AM
To: 'RPG programming on the IBM i / System i'
Subject: Safe to maintain pointer to errno() ?

Folks, I have often wondered and have never found reference to the internal workings of errno. My specific question is whether it is safe to obtain a pointer to errno only one time, and then reference the based value from then on. It makes sense to me that errno's value would be at a static location and won't float around in memory, but - again - I haven't seen any guarantee of that. So in my programs every time I want to measure success of certain operations, it's the old retrieve-the-address-and-test-the-value approach.
This really is like the C approach except that in C it can be a single instruction ( if (*errno < 1) . ).



Any takers from folks in the know?



Dennis E. Lovelady
AIM/Skype: delovelady MSN: fastcounter@xxxxxxxxxxxx
<http://www.linkedin.com/in/dennislovelady>
www.linkedin.com/in/dennislovelady --
Using Windows is better than eating glass*
- *Depending upon the quality of the glass.



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