tavianator added a comment.
In https://reviews.llvm.org/D21803#532309, @EricWF wrote:
> `__thread`
>
> What do you think of this idea?
Makes sense to me, I'll integrate it into the next revision.
================
Comment at: src/cxa_thread_atexit.cpp:42
@@ +41,3 @@
+ // - thread_local destructors on other threads run on the first iteration
+ // through the pthread_key destructors. std::notify_all_at_thread_exit()
+ // and similar functions must be careful to wait until the second iteration
----------------
EricWF wrote:
> Can you clarify what you mean by "other threads"?
>
> How is libc++ supposed to detect and handle this problem?
I meant "non-main threads" ("other" is in relation to the bullet point above),
but I can clarify this, sure.
libc++ could be patched to do something like this:
```
pthread_key_t key1, key2;
void destructor1(void* ptr) {
pthread_setspecific(key2, ptr);
}
void destructor2(void* ptr) {
// Runs in the second iteration through pthread_key destructors,
// therefore after thread_local destructors
}
pthread_key_create(&key1, destructor1);
pthread_key_create(&key2, destructor2);
pthread_setspecific(key1, ptr);
```
(Or it could use a counter/flag and a single pthread_key.)
libstdc++ has the same bug when __cxa_thread_atexit_impl() isn't available, so
I'm not sure that change would really be necessary. If it is, I can write up
the libc++ patch.
https://reviews.llvm.org/D21803
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