Hajo Münzer wrote:
Is this defined somewhere in the C++ standard (where?) or is this gcc
specific? I was told that e. g. in MS Visual C++ 0xffffffff is
interpreted as -1.
In ISO/IEC 9899:201x (i.e. C99)
Under 6.25 Types
16 An enumeration comprises a set of named integer constant values. Each
distinct
enumeration constitutes a different enumerated type.
Under 6.7.2.2 Enumeration specifiers
4 Each enumerated type shall be compatible with char, a signed integer
type, or an
unsigned integer type. The choice of type is
implementation-defined,113) but shall be
capable of representing the values of all the members of the
enumeration. The
enumerated type is incomplete until after the } that terminates the
list of enumerator
declarations.
113) An implementation may delay the choice of which integer type until
all enumeration constants have
been seen.
Which obviously leaves much up to the compiler.
In ISO/IEC 14882, Programming language – C++ (from a ballot of October
2008).
Under 3.9.1 Fundamental types
7 Types bool, char, char16_t, char32_t, wchar_t, and the signed and
unsigned integer types are collectively
called integral types.44
44) Therefore, enumerations (7.2) are not integral; however,
enumerations can be promoted to integral types as specified in 4.5.
Under 4.5 Integral promotions
2 ...
An rvalue of an
unscoped enumeration type (7.2) can be
converted to an rvalue of the first of the following types that can
represent all the values of the enumeration
(i.e. the values in the range bmin to bmax as described in 7.2): int,
unsigned int, long int, unsigned
long int, long long int, or unsigned long long int. If none of the
types in that list can represent all
the values of the enumeration, an rvalue of an unscoped enumeration
type can be converted to an rvalue of
the extended integer type with lowest integer conversion rank (4.13)
greater than the rank of long long in
which all the values of the enumeration can be represented. If there
are two such extended types, the signed
one is chosen.
So as you see it's clearly specified in C++.
Patrick
