[Libguestfs] [hivex] Segfault for an integer value to node_set_value

[Hilko Bengen]

* Peter Wu:

> When an integer argument is passed as value, node_set_value
> segfaults. Reproducer is at the end of this message

Uh-oh. It looks like the handling of values is broken for non-string
cases.

    bytes = PyUnicode_AsUTF8String (obj);

with obj derived from the numeric 1234 causes bytes to be set to null.
A line of error handling code tells us why:

    TypeError: bad argument type for built-in operation

For Python2, ret->len is set to a value that is too large for size_t,
and thus malloc(), so Python crashes with...

    RuntimeError: Cannot allocate memory

I am looking at fixing this.

Cheers,
-Hilko