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Re: [ub] [c++std-ext-14555] Sized integer types and char bits

From: Matt Austern <austern_at_[hidden]>
Date: Fri, 18 Oct 2013 12:54:38 -0700
On Fri, Oct 18, 2013 at 12:05 PM, Stephan T. Lavavej <
stl_at_[hidden]> wrote:

> [Gabriel Dos Reis, c++std-ext-14555]
> > My understanding of 'optional' is that the types are conditionally
> > supported, and a macro in <stdint.h> indicates whether the corresponding
> > type is supported.
> They are a special form of conditionally supported. C99
> "Exact-width integer types" /3: "These types are optional. However, if an
> implementation provides integer types with widths of 8, 16, 32, or 64 bits,
> no padding bits, and (for the signed types) that have a two's complement
> representation, it shall define the corresponding typedef names."
> I would like to see CHAR_BIT == 8 and two's complement required. I do not
> want to see specific type requirements for intN_t (in fact, char is
> impossible because it can be either signedish or unsignedish).

And as far as I can tell, int8_t is forbidden to be char even on a system
where char can represent negative numbers. The standard says that int8_t
must be a "signed integer type". Even though char is an integer type that
is signed on some implementations, my reading of the standard is that it is
not a signed integer type. That term refers to a specific list of types and
char does not appear on that list.


Received on 2013-10-18 21:54:40