User Extensions, TCB Extension area, and TCBs in general

[Wu, Mark H.]

Sorry to revive an old thread, but I have a question that may solve my confusion here. When I call rtems_extension_create(), does this add or replace the current extension set? My interpretation from the documentation was that it replaced the set, but looking through some of the source code, it appears that it might actually add to the set? So if I add stack bounds checking, I don't actually have to worry about re-adding it to any new extension sets? If that's the case, then it fully addresses all of my concerns!

It looks like the order of calling the extensions is in the order they were created. Is that correct? 

-----Original Message-----
From: Sebastian Huber [mailto:sebastian.huber at embedded-brains.de] 
Sent: Monday, May 18, 2015 00:09
To: Wu, Mark H.; users at rtems.org
Subject: Re: User Extensions, TCB Extension area, and TCBs in general

On 15/05/15 16:46, Wu, Mark H. wrote:
> I understand that you use rtems_extension_create(), but some of that is done "quietly." Specifically, the static extension set is created by configure, and the stack bounds checking is created similarly (if you use the mechanism described in the documentation). How do I get the object identifiers that are created/returned by that configuration/initialization code?

The statically configured extensions have no object identifier and there 
is no field for them in the TCB. If you use the Git master on ARM, 
PowerPC or SPARC, then I would use thread-local storage for your extension.

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