Re: Safe to maintain pointer to errno() ?

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) . ).