The implementation of sleep() looks like a game of Seastar golf - doing
something in the minimum number of lines possible :-) Unfortunately, it
looks very clever, but not quite right. sleep() usually works correctly,
but the sanitizer (in the debug build) catches a use after free.
The problem was that we delete an object which contains a timer which
contains the callback (and std::function) - from inside this callback.
The workaround in this patch is to use our future chaining to only delete
the sleeper object after its future became ready - and at that point, none
of the sleeper object or code is needed any more.
This patch also includes a regression test for this issue. The test looks
silly (just sleeps and checks nothing), but in the debugging build it
failed (with a sanitizer reporting use-after-free) before this patch.
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
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