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Date: Sun, 22 Nov 2015 18:25:09 -0500
From: Matthew Hall <mhall@mhcomputing.net>
To: Thomas Monjalon <thomas.monjalon@6wind.com>
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Subject: Re: [dpdk-dev] difficulty w/ RTE_NEXT_ABI
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On Sun, Nov 22, 2015 at 09:59:30PM +0100, Thomas Monjalon wrote:
> > So again I am confused what advantage we got from RTE_NEXT_ABI here, and how 
> > you have multiple copies of RTE_NEXT_ABI on a single symbol when it is a 
> > binary variable.
> 
> I don't understand what is not clear here.

OK. Let me restate it.

I was starting from an assumption that the purpose of RTE_NEXT_ABI was to 
allow ABI changes.

In most projects I worked on, a renaming of a variable when the data type is 
unchanged does not count as an ABI change. So it seems like this is different 
from the usual definition.

Secondly, if one is making an ABI change, like I was, to some code which was 
already changed once using RTE_NEXT_ABI, which part of the code do you change?

Do you make a third copy different from the first two copies? If you make a 
third copy, but RTE_NEXT_ABI is binary (i.e. it has two values, on and off) 
then what labeling do you apply to the third copy?

If you don't make a third copy, I am assuming you edit the copy marked with 
RTE_NEXT_ABI. But then what happens to a downstream user who wants to have 
RTE_NEXT_ABI with the first ABI change, and not your second ABI change?

Can you see what I am trying to ask now?

Matthew.