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Re: [libvirt] [PATCH] python: improve conversion validation



On 03/30/12 20:49, Eric Blake wrote:
> Laszlo Ersek pointed out that in trying to convert a long to an
> unsigned int, we used:
> 
> long long_val = ...;
> if ((unsigned int)long_val == long_val)
> 
> According to C99 integer promotion rules, the if statement is
> equivalent to:
> 
> (unsigned long)(unsigned int)long_val == (unsigned long)long_val
> 
> since you get an unsigned comparison if at least one side is
> unsigned, using the largest rank of the two sides; but on 32-bit
> platforms, where unsigned long and unsigned int are the same size,
> this comparison is always true and ends up converting negative
> long_val into posigive unsigned int values, rather than rejecting
> the negative value as we had originally intended (python longs
> are unbounded size, and we don't want to do silent modulo
> arithmetic when converting to C code).
> 
> Fix this by using direct comparisons, rather than casting.
> 
> * python/typewrappers.c (libvirt_intUnwrap, libvirt_uintUnwrap)
> (libvirt_ulongUnwrap, libvirt_ulonglongUnwrap): Fix conversion
> checks.

I know I'm late but

ACK

Thanks,
Laszlo


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