[Bug 1001344] Allow nc_test_slave for lwIP to compile for targets with 128KiB RAM.

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--- Comment #30 from Ilija Kocho <ilijak@siva.com.mk> 2012-05-26 20:19:15 BST ---
(In reply to comment #29)
> (In reply to comment #28)
> > 
> > > I think that "volatile" is strong enough so compiler wouldn't dare to drop
> > > it even for an automatic variable.
> 
> I know that isn't always true. For example, if you call
> do_some_random_computation with a constant, gcc will optimise away the
> calculation. And with some code, gcc may be able to optimise expressions into
> constants that you may not expect it to be able to - it doesn't have to be a
> literal constant, but an expression gcc has worked out can only have one value.
> 
> For the case of nc_test_slave.c it does appear to be fine for that particular
> case - it's not called with a constant. But my point is that your statement is
> not generally true that volatile is guaranteed to be respected. And if it isn't
> generally true, what guarantee do we have that it will remain true in the case
> of nc_test_slave.c's use of it as well.
> 
> Anyway...
> 

I haven't encountered such case but I do dump checking whenever I have some
doubt.

> > > I wonder if you can use both USED and UNUSED at the same time. Given their
> > > intended functions, you should be able to, despite the English meanings
> > > implying they are in some way opposites to each other. That would deal with the
> > > uncertainty.
> > 
> > Then we get ...warning: ‘used’ attribute ignored... as per Comment #26.
> 
> In that case we'll have to trust the GCC people will indeed continue to respect
> the volatile because we don't seem to have any alternative.
> 

FAOD, are we go for commit?

Sergei, FYI it works on synthetic target too.

Ilija

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