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.

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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

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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 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.

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