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NNTP-Posting-Date: Tue, 09 May 2017 12:30:46 -0500
From: Gareth Owen <gwowen@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: gcc failure (optimised/non-optimised)
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Date: Tue, 09 May 2017 18:30:46 +0100
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Xref: csiph.com comp.lang.c:109608

David Brown <david.brown@hesbynett.no> writes:

> On 08/05/17 18:16, supercat@casperkitty.com wrote:
>> On Monday, May 8, 2017 at 9:21:09 AM UTC-5, David Brown wrote:
>>> "some_value" is not volatile, and the compiler can see it is never
>>> changed.  Why should it reload it?  Is the compiler to guess what you
>>> meant to write?  I suppose /I/ should have been able to guess what you
>>> meant, but I often find it hard with your examples.
>>
>> On many systems, data is read or written by giving some outside process the
>> address if the data and performing a write to a volatile location to trigger
>> that process.  It is not unusual for the act of writing to a volatile location
>> to affect other aspects of system state.
>
> Yes, it is unusual.  The code is wrong - it is incorrect C.  Maybe you
> are used to writing such code, but /I/ certainly am not.

Now we get to the nub.  Supercat has been writing that incorrect code
for decades, and it used to kind-of-mostly-work and he is /pissed/ that
everyone else refuses to be constrained by his ingrained misconceptions.