tree 8074d1fcab89c29e08bef00f2555082393a3560d
parent 5d0efb7d523dff64c34320f36082b3ff04e096e2
author Willy Tarreau <w@1wt.eu> 1649941242 +0200
committer Christopher Faulet <cfaulet@haproxy.com> 1650962384 +0200

BUILD: sched: workaround crazy and dangerous warning in Clang 14

Ilya reported in issue #1638 that Clang 14 has invented a new warning
that encourages to modify the code in a way that is not always
equivalent, by turning "|" to "||" between some logical operators,
except that the first one guarantees that all members of the expression
will always be evaluated while the latter will stop at the first one
which is true!

This warning triggers in thread_has_tasks(), which is not sensitive to
such change of behavior but which is built this way because it results
in branchless code for something that most often evaluates to false for
all terms. As such it was out of question to turn this to less efficient
compare-and-jump that needlessly pollute the branch predictor, so the
workaround consists in casting each expression to (int). It was verified
that the code is the same.

Yet another example of how-to-introduce-bugs-by-fixing-valid-code
through warnings invented around a beer without thinking longer!

This may need to be backported to a few older branches in case this
compiler lands in recent distros or if gcc finds it wise to imitate it.

(cherry picked from commit e1efd2a2d7518c05c78dd870999201582b1e0fc7)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 8cdf4d1cf08efb7eff9edbb2da2cc1fcbbcb05d4)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>