GCC 3.3.1, new warnings with <limits>

[David Leimbach]

On Sunday, July 13, 2003, at 1:23PM, M. Warner Losh wrote:

> : >     134 #define __glibcpp_signed(T)     ((T)(-1) < 0)
> : #define __glibcpp_signed(T)     (!((T)(-1) > 0))
>
> Why not the simpler:
>
> #define __glibcpp_signed(T)     ((T)(-1) <= 0)
>
> that way we have an overlap on the range of the two types, so we won't
> get a warning.  We know for a fact that -1 != 0 for all known machine
> types (all machines are two's complement, or are required to behave as
> if they are two's complement, per the standard).
>

You keep saying this... where is this "must behave as two's compliment 
stated?"


> (unsigned int) -1 == 0xffffffff	  (assuming 32-bit int).

or with a valid one's compliment C99 compliant system
(unsigned int) -1 = 0xfffffffe;

>
> even on a one's complement's machine, without the standard conversion,
> the 'type punning' conversion of -1 would yield 0xfffffffe, which is
> still > 0.
>
Correct :).  I still don't think C enforces two's compliment.

Dave

> Warner
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