Re: [PATCH] "volatile considered harmful", take 3

Satyam Sharma wrote:

Because volatile is ill-defined? Or actually, *undefined* (well,
implementation-defined is as good as that)? It's *so* _vague_,
one doesn't _feel_ like using it at all!


Sorry, that's just utter crap. Linux isn't written in some mythical C
which only exists in standard document, it is written in a particular
subset of GNU C. "volatile" is well enough defined in that context, it
is just frequently misused.

We already have a complete API containing optimization barriers,
load/store/full memory barriers. With well-defined and
well-understood semantics. Just ... _why_ use volatile?

See below.

It will _always_ work. In fact you can't really say the same for
volatile. We already assume the compiler _actually_ took some
pains to stuff meaning into C's (lack of) definition of volatile and
implement it -- but in what sense, nobody knows (the C standard
doesn't, so what are we).

It will always work within the context of GNU C.

more heavy-handed as it's disabling *all* optimization such as loop
invariants across the barrier.

This is a legitimate criticism, I agree.

There you have it.

-hpa
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