Re: Help with bit-field semantics in C and C++

[Mike Stump <mrs at apple dot com>]

On Tuesday, August 24, 2004, at 01:12  PM, Gabriel Dos Reis wrote:
> The underlying type of E needs only be an integer type large enough to
> contain a data expressible with a single bit

7 Types bool, char, wchar_t, and the signed and unsigned  integer  types
  are collectively called integral types.43) A synonym for integral type
  is integer type.  The representations of integral types  shall  define
  values by use of  a pure binary numeration system.44)  [Example:  this
  International  Standard  permits  2's  complement,  1's complement and
  signed magnitude representations for integral types.  ]

5 The underlying type of an enumeration is an  integral  type  that  can
  represent all the enumerator values defined in the enumeration.  It is
  implementation-defined which integral type is used as  the  underlying
  type  for  an enumeration except that the underlying type shall not be
  larger than int unless the value of an enumerator cannot fit in an int
  or unsigned int.  If the enumerator-list is empty, the underlying type
  is as if the enumeration had a single enumerator with  value  0.   The
  value of sizeof() applied to an enumeration type, an object of enumer-
  ation type, or an enumerator, is the value of sizeof() applied to  the
  underlying type.

The intent of the standard is not to confuse bool into this...  
Therefore, the underlying type of enum { foo } can be char. a signed 
integer type or an unsigned integer type.  We can see this by using 
using enum { foo = 3 } e in the analysis.  Either, we come up with

e = 7;
if (e == 7) ...

mandated to equal 7, or we don't.  I contend the standard mandates it 
be 7.  I contend that the way you are presenting this is at best 
misleding, and that it what I am objecting to.

Also, bools can take on values that are neither true nor false.