abstract_th : segfault when the program halts

[jflesch]

When a program uses abstrat_th and halts, it segfaults.

What happens:

• The main thread of the program disappear
• The Sane thread decided to halt
• When X tries to cleanup everything that belongs to the Sane thread, the Python interpreter segfault

The problem comes from either libsane + threads or ctypes + threads.

This is a really minor issue, since the program is pretty much finished when it happens. Still, segfaults are not good features :p

[jflesch]

The problem only occurs if sane_exit() is called. It looks like in some cases, if sane_exit() is called at some point, when the program exists, Sane data are cleaned a second time --> double-free/whatever --> segfault.

I don't know well enough Sane to dig further. --> Workaround added : d3de44473c04723cf84907ee050faa8d0a24691c

[jflesch]

Workarounded by abstract_proc anyway.