I can't disagree with your reading ("involve" doesn't mean "be"). However,
searching for "integral constant expression" suggests to me that this
outlaws the following code, all of which compiles without warning:
enum {dim = 1};
char a [dim]; // 8.3.4.1
void* b = new char [1] [dim]; // 5.3.4.6
struct Badger
{
static const int i = dim; // 9.4.2.4
};
-----Original Message-----
From: Martin v. Loewis [mailto:[EMAIL PROTECTED]
Sent: Wednesday, October 24, 2001 9:09 AM
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED];
debian-gcc@lists.debian.org; [EMAIL PROTECTED]
Subject: Re: comparing function pointer with int does not produce error
> > I'll take another attempt at declaring gcc behaviour to be correct.
> > According to 4.10/1, "success" is a null pointer constant:
> >
> > # A null pointer constant is an integral constant expression (5.19)
> > # rvalue of integer type that evaluates to zero. A null pointer
> > # constant can be converted to a pointer type; the result is the null
> > # pointer value of that type and is distinguishable from every other
> > # value of pointer to object or pointer to function type.
> >
> > 5.19/1 defines "integral constant expressions":
> >
> > # An integral constant-expression can involve only literals (2.13),
> > # enumerators, const variables or static data members of integral or
> > # enumeration types initialized with constant expressions (8.5),
> > # non-type template parameters of integral or enumeration types, and
> > # sizeof expressions.
>
> Then why does the following NOT compile:
>
> void stat ();
> enum {success};
> void monk ()
> {
> if (stat == success);
> }
>
> cbool.cpp:6: no match for `void (&)() == <anonymous enum>' operator
>
> As success is an enumerator which is a integral constant-expression by
your
> definition above; it also has zero value and thus must be a "null pointer
> constant" and hence the comparisom should be allowed (however distasteful
> that may be).
In this code, "success" does not have integer type. 3.9.1/7 specifies
# Types bool, char, wchar_t, and the signed and unsigned integer types
# are collectively called integral types. A synonym for integral type
# is integer type.
Since a null pointer constant must be of integer type, "success" does
not qualify. Change it to "(int)success", and it compiles.
Regards,
Martin
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