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Re: [Qemu-block] [Qemu-devel] [PATCH v3 2/5] qapi: Add qobject_is_equal(


From: Eric Blake
Subject: Re: [Qemu-block] [Qemu-devel] [PATCH v3 2/5] qapi: Add qobject_is_equal()
Date: Wed, 5 Jul 2017 12:18:07 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0

On 07/05/2017 12:00 PM, Max Reitz wrote:
>> (uint64_t)(UINT64_MAX + 1) is well-defined - it is 0.
>>
>> (Adding in unsigned integers is always well-defined - it wraps around on
>> mathematical overflow modulo the integer size.  You're thinking of
>> overflow addition on signed integers, which is indeed undefined)
> 
> It's not. See the standard:
> 
> When a finite value of real floating type is converted to an integer

Ah, you're talking:

(uint64_t)(double)(UINT64_MAX + 1), which is indeed undefined.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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