GCC 3.3.1, new warnings with <limits>
leimy2k at mac.com
Sun Jul 13 11:25:58 PDT 2003
On Sunday, July 13, 2003, at 1:11PM, M. Warner Losh wrote:
> In message: <20030713152154.GA96653 at stack.nl>
> Jilles Tjoelker <jilles at stack.nl> writes:
> : The compiler moans about (T)(-1) >=3D 0 as well. Is the assumption =
> : (unsigned type)(-1) is never zero valid?
> yes. There are no known machines where -1 =3D=3D 0 for types of =
> signs. Further, the C standard says that it must behave as if it is a
> two's complement machine, and I think that C++ says so too.
I am pretty certain you can do one's compliment in the C99 standard,=20
some of that is implementation/platform dependant.
See section 22.214.171.124 of the C99 standard which enumerates the following 3
negative number representations:
=A1Xthe corresponding value with sign bit 0 is negated (sign and=20
=A1Xthe sign bit has the value-(2^N )(two=A1=A6s complement);
=A1Xthe sign bit has the value-(2^N -1) (one=A1=A6s complement).
"Which of these applies is implementation-defined, as is whether the=20
value with sign bit 1 and all value bits zero (for the first two), or=20
with sign bit and all value bits 1 (for one=A1=A6s complement), is a =
representation or a normal value. Inthe case of sign and magnitude and=20=
one=A1=A6scomplement, if this representation is a normal value it is =
a negative zero. "
Yes... a negative 0.
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