I don't follow MW logic at all. Casting and automatic integer
conversion are both clearly spec'ed in the ANSI document. Is someone at
MW saying that when the cast occurs in relationship to the integration
of the casted operand occurs is unspecified? If so, that person is
incorrect.
-jjf
-----Original Message-----
From: Jun-Kiat Lam [mailto:[EMAIL PROTECTED]]
Sent: Thursday, February 17, 2000 9:13 AM
To: Palm Developer Forum
Subject: Re: CW6 optimizer bug?
Man, y'all really started a firestorm here at MW....:-)
After a small spirited discussion, it looks like it is not a bug after
all.
Given an expression like:
return x + (signed long) (y - z) * 10;
ANSI 6.3.3:
"Except as indicated by the syntax or otherwise specified later (for the
function-call operator (), &&, ||, ?: and comma operators) the order of
evaluation of subexpressions and the order in which side effects take
place
are both unspecified"
Footnote 57:
"This paragraph renders undefined statement expressions such as
i = ++i + 1;
while allowing
i = i + 1;"
So the result of the above expression is undefined.
Hope this helps.
Jun-Kiat Lam
Metrowerks Technical Support
----- Original Message -----
From: "Nathan J. Williams" <[EMAIL PROTECTED]>
To: "Palm Developer Forum" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Wednesday, February 16, 2000 9:40 PM
Subject: Re: CW6 optimizer bug?
> Marshall Clow <[EMAIL PROTECTED]> writes:
>
> > >Not quite. The conversion from unsigned to signed int *is*
well-defined.
> >
> > For some implementations.
>
> For any implementation that conforms to ANSI. Random non-conforming
> implementations are out of scope.
>
> >
> >
> > >Chapter and verse: ANSI, 3.2.1.2, lines 23-27:
> ...
> >
> > And if the unsigned integer does not have greater size?
>
> Next paragraph:
>
> "When a value with integral type is demoted to an unsigned integer
> with smaller size, the result is the nonnegative remainder on division
> by the number one greater than the largest unsigned number that can be
> represented in the type with the smaller size."
>
> > >So an expression like "(unsigned int) 1 + -10" is officially
> > >well-defined and has the value UINT_MAX - 8.
> >
> > Assuming two's-complement representation.
>
> No, see what I wrote before. The spec requires the behaviour of
> two's-complement representation even for systems with other underlying
> representations. From the Rationale for the same section:
>
> "Precise rules are now provided for converting to and from
> unsigned integers. On a twos-complement machine, the operation is
> still virtual (no change of representation is required), but the
> rules are now stated inependent of representation."
>
> - Nathan
>
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