Re: [Qemu-devel] [PATCH 1/2] hmp: expr_unary(): check for overflow in strtoul()

[Eric Blake]

On 04/26/2012 05:18 PM, Luiz Capitulino wrote:
>> Not quite right.  ULLONG_MAX is a valid return, but you did not prime
>> errno, so if errno has junk ERANGE from some earlier point in the
>> program, you will have a false negative.  You are guaranteed that errno
>> is unchanged on success, so prime things by setting errno to 0 before
>> calling strtoull.
> 
> I thought about doing that but - hope that won't sound stupid - how can I
> guarantee that ERANGE is not 0?

Because POSIX requires that all E* constants are positive numbers,
reserving errno of 0 for success.

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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