Re: port-hp300/50852: src/sys/arch/hp300/stand/common/ite.c:239: bad expression

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Fri, Feb 26, 2016 at 05:04:46PM -0600, Dave Huang wrote:
> On Fri, Feb 26, 2016 at 09:24:14PM +0100, Joerg Sonnenberger wrote:
> > On Fri, Feb 26, 2016 at 04:45:21PM +0000, David Binderman wrote:
> > > >> Source code is
> > > >>
> > > >> whichconsole = ++whichconsole % (NITE+1);
> > > >>
> > > >> Maybe better code
> > > >>
> > > >> whichconsole = (whichconsole + 1) % (NITE+1);
> > > >
> > > > Independent of the question of which code is better, I don't think the
> > > > error is correct. 
> > > 
> > > False, the error is valid.
> > > 
> > > There are two writes to whichconsole, one on the left of the assignment,
> > > one on the right.
> > > 
> > > The ISO standard doesn't define which order those writes occur.
> > > See Steve Summit's C FAQ for sequence points, section 3.8.
> > 
> > You are wrong. There is no write from the left operand of the
> > assignment. The write is the result of the assignment and as written
> > before is explicitly sequenced by the standard.
> 
> How is the code in question different from i = ++i;, which I've always
> been told is undefined? The assignment operator does not introduce a
> sequence point.

At least in C11, it does.

Joerg