On 2014-04-01, 6:59 PM, Benoit Jacob wrote:
2014-04-01 18:40 GMT-04:00 Jeff Walden <jwalden+...@mit.edu>:
On 04/01/2014 02:32 PM, Ehsan Akhgari wrote:
What do people feel about my proposal? Do you think it improves writing
and reviewing thread safe code to be less error prone?
As I said in the bug, not particularly. I don't think you can program
with atomics in any sort of brain-off way, and I don't think the
boilerplate difference of += versus fetch-and-add or whatever really
affects that. To the extent things should be done differently, it should
be that *template* functions that deal with atomic/non-atomic versions of
the same algorithm deserve extra review and special care, and perhaps even
should be implemented twice, rather than sharing a single implementation.
And I think the cases in question here are flavors of approximately a
single issue, and we do not have a fundamental problem here to be solved by
making the API more obtuse in practice.
How are we going to enforce (and ensure that future people enforce) that?
(The part about "functions that deal with atomic/non-atomic versions of the
same algorithm deserve extra review and special care") ?
My proposal would enforce that!
I like Ehsan's proposal because, as far as I am concerned, explicit
function names help me very well to remember to check atomic semantics;
especially if we follow the standard <atomic> naming where the functions
start by atomic_ , e.g. std::atomic_fetch_add.
On the other hand, if the function name that we use for that is just
"operator +" then it becomes very hard for me as a reviewer, because I have
to remember checking everytime I see a "+" to check if the variables at
hand are atomics.
Just to clarify my position a bit more, I think criticizing my position
by pretending that I'm advocating for a brain-off way of programming
with atomics is a bit contrived. I definitely understand that atomics
require special feeding and care. What's under debate is whether we
should make that obvious to authors and reviewers by not conflating
things such as operator++ etc. to work on both atomic and non-atomic types.
Cheers,
Ehsan
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