1501
   k my interpretation of the condition for forwarding the defaults to the
   backend a second time in libusb_init was incorrect
   in f7084 by harbulot, the condition is changed from (!ctx) to (ctx ||
   !usbi_default_context)
   this results in forwarding the values when there is a ctx, which wasn't
   previously the case.
   there might be a logic error here regarding default ctxs?  i'll
   increase git's diff output
   1513
   1517
   ok
   in libusb_init, ctx is the pointer-to-a-pointer passed in.  nowadays if
   it is null, a default context is supposedly used.
   meanwhile _ctx with its preceding underscore, is a zero initialised
   block of memory that will be the new ctx, allocated on the heap.  it
   looks like this memory is allocated even if a default context might be
   reused.
   it looks like a logic bug may be present.  it appears that
   usbi_default_context is uninitialised, so likely default_context_refcnt
   should be checked rather than it.
   1521
   default_context_refcnt is also uninitialised.  it would make sense to
   fix these.
   I wonder if c supports static local variables.  I guess I should maybe
   know that whether it's relevant or not.
   looks like they are.  1524.  should be accessed with lock I imagine.  I
   think there's some existing static locked stuff, unsure, can see what
   degree of protection against initialisation order they're using.
   I think they have a list of contexts maybe?  unsure?
   oh great there's a default_context_lock
   and an active_contexts_list
   interestingly the check already compares the content of the structure
   with zero.  I wonder if things are auto filled with zeros.
   it just contains two pointers, prev and next.
   maybe websearching can help me
   1528
   the internet does not yet appear to believe that happens.  maybe they
   use some compile flag, i'll glance at them.
   they pass -std=gnu11
   maybe i'll glance through c11 stuff and websearch more
   1531
   ok at [1]journaldev.com I found "The default value of the
   initialization of the Static variable is zero (0)."  maybe I can find
   something more authoritative
   ok I found a second source saying static and global variables are
   initialised to zero if not initialised explicitly.  so I better
   reconsider this code, which looks much better now.
   1534

References

   1. http://journaldev.com/