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work around portability issue on FreeBSD, in which the key returned from

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pthread_key_create can be 0.
This commit is contained in:
Aidan Cully 2014-12-05 17:20:44 -05:00
parent 95d1771139
commit 7bf7bd6a75
1 changed files with 17 additions and 1 deletions
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18
src/libstd/sys/common/thread_local.rs
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@ -185,7 +185,23 @@ impl StaticKey {
}
unsafe fn lazy_init(&self) -> uint {
let key = imp::create(self.dtor);
// POSIX allows the key created here to be 0, but the compare_and_swap
// below relies on using 0 as a sentinel value to check who won the
// race to set the shared TLS key. As far as I know, there is no
// guaranteed value that cannot be returned as a posix_key_create key,
// so there is no value we can initialize the inner key with to
// prove that it has not yet been set. As such, we'll continue using a
// value of 0, but with some gyrations to make sure we have a non-0
// value returned from the creation routine.
// TODO: this is clearly a hack, and should be cleaned up.
let key1 = imp::create(self.dtor);
let key = if key1 != 0 {
key1
} else {
let key2 = imp::create(self.dtor);
imp::destroy(key1);
key2
};
assert!(key != 0);
match self.inner.key.compare_and_swap(0, key as uint, atomic::SeqCst) {
// The CAS succeeded, so we've created the actual key