Re: Safe to maintain pointer to errno() ?

[Jon Paris <jon.paris@xxxxxxxxxxxxxx>]

When I first started experimenting with calling C functions from RPG  
back before V3R2 came out I asked the guys on the C compiler team  
about this. The answer I got was that for "historical" reasons it  
could not be guaranteed. I know that the C compiler and run time has  
changed since then, so it is possible that this is no longer true, but  
I never risk it. Barbara may know for sure.


Jon Paris

www.Partner400.com
www.SystemiDeveloper.com



On Oct 13, 2010, at 1:00 PM, rpg400-l-request@xxxxxxxxxxxx wrote:

> 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) . ).