sipa commented on this pull request.
+ * TODO: using thread_local changes the abi in ways that may not play nice
+ * when the c++ stdlib is linked dynamically. Disable it until thorough
+ * testing has been done.
+ * mingw32’s implementation of thread_local has also been shown to behave
+ * erroneously under concurrent usage; see:
+ * https://gist.github.com/jamesob/fe9a872051a88b2025b1aa37bfa98605
Unsure if we should have the code in in that case, as it’s untestable (it also doesn’t compile currently).