Ensure ruby_xfree won't segfault if called after vm_destruct

[Bug #19580]

The real-world scenario motivating this change is libxml2's pthread
code which uses `pthread_key_create` to set up a destructor that is
called at thread exit to free thread-local storage.

There is a small window of time -- after ruby_vm_destruct but before
the process exits -- in which a pthread may exit and the destructor is
called, leading to a segfault.

Please note that this window of time may be relatively large if
`atexit` is being used.

0 files changed, 0 insertions, 0 deletions