[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <8760f5s7o8.fsf@gmail.com>
Date: Thu, 06 Jul 2017 21:10:31 +0200
From: Leah Neukirchen <leah@...u.org>
To: Bartosz Brachaczek <b.brachaczek@...il.com>
Cc: musl@...ts.openwall.com
Subject: Re: Documentation of memcpy and undefined behavior in memset
Bartosz Brachaczek <b.brachaczek@...il.com> writes:
> On 7/6/2017 6:23 PM, Rich Felker wrote:
>> I think you're correct, at least under a pessimistic interpretation of
>> the standard. I can't find where they actually define "modifies", and
>> you could argue that assignment of the same value twice "modifies" the
>> object at most once, but I don't like relying on that kind of
>> ambiguity and it's easy enough to fix just by adding a sequence point.
>
> I don't have a copy of C11, but N1570 reads in a note to 3.1:
>
>> ‘‘Modify’’ includes the case where the new value being stored is the
>> same as the previous value.
C11 also specifies a sequence for assignment (6.5.16.3):
> The side effect of updating the stored value of the left operand is
> sequenced after the value computations of the left and right
> operands.
--
Leah Neukirchen <leah@...u.org> http://leah.zone
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
