On 05/09/2016 04:32 PM, Nicholas Nethercote wrote:
On Sat, Apr 23, 2016 at 9:29 AM, Nicholas Nethercote
<[email protected]> wrote:
one thing I've been thinking about is using
MOZ_WARN_UNUSED_RESULT more.
It isn't useful for the "return null on failure" case, because the
result will always be used even if you forget the check. But it is
useful for the "return false on failure" case. I count 113 uses of it
currently in js/src/, the majority of which are for functions
returning bool. I suspect the number could/should be at least 10x
higher than that.
I would be happy to try to add more uses of it if people think it's worthwhile.
I've started doing this in bug 1267551. (Taking over from bug 606349,
where this idea was first suggested.)
Having added quite a few MOZ_MUST_USE annotations now I can't help but
wonder if it would be better to have some kind of result type
(JSResult?), as an alternative to bool. A bit like nsresult but
without the zillion different failure values.
With that in place, bool would be used for the return type of
functions to indicate true/false or yes/no, and JSResult would be used
in fallible functions to indicate success/failure. And then we could
use MOZ_MUST_USE_TYPE on JSResult, which would give us assurance (via
static analysis) that all functions that return this type are checked,
and then we wouldn't need all these MOZ_MUST_USE annotations
everywhere.
JSBool is dead, long live JSBool!
(We might also need a JSResultUnchecked variant, because for some
fallible functions not checking the return value is reasonable.)
With JSBool, we could call this one 'bool'.
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