A TLS slot for values of type 'a. This allows the storage of a single value of type 'a per thread.

Allocate a new TLS slot. The TLS slot starts uninitialised on each thread.

Note: each TLS slot allocated consumes a word per thread, and it can never be deallocated. create should be called at toplevel to produce constants, do not use it in a loop.

• raises Failure

  if no more TLS slots can be allocated.

Exception raised when accessing a slot that was not previously set on this thread

get_exn x returns the value previously stored in the TLS slot x for the current thread.

This function is safe to use from asynchronous callbacks without risks of races.

• raises Not_set

  if the TLS slot has not been initialised in the current thread. Do note that this uses raise_notrace for performance reasons, so make sure to always catch the exception as it will not carry a backtrace.

get_opt x returns Some v where v is the value previously stored in the TLS slot x for the current thread. It returns None if the TLS slot has not been initialised in the current thread.

This function is safe to use from asynchronous callbacks without risks of races.

get_default x ~default returns the value previously stored in the TLS slot x for the current thread. If the TLS slot has not been initialised, default () is called, and its result is returned instead, after being stored in the TLS slot x.

If the call to default () raises an exception, then the TLS slot remains uninitialised. If default is a function that always raises, then this function is safe to use from asynchronous callbacks without risks of races.

• raises Out_of_memory

set x v stores v into the TLS slot x for the current thread.

• raises Out_of_memory