This is the mail archive of the mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: g++4.0 diagnostic on casting a static const member initializer to a double

On Jan 31, 2005, at 10:16 AM, Mark Mitchell wrote:

Fariborz Jahanian wrote:
g++ 4.0 in FSF issues a diagnostic on the following test case:
template <class T> struct S {
static const double scd = (double)24;
test1.C:2: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
Rewriting the above to:
template <class T> struct S {
static const double scd;
template <class T>
const double S<T>::scd = (double)24;
Compiles. Event though the diagnostic is clear in what it is saying, but it seems to be a g++ bug
one way or the other.

No, the input program is invalid. From []:

"If a static data member is of const integral or const enumeration type, its declaration in the class definition can specify a constant-initializer which shall be an integral constant expression(_expr.const_)."

The diagnostic could be better, but it is indeed accurate; if there's an initializer it must be integral constant-expression, and a cast to "double" cannot appear in such an expression.

Hm, I think it's stretching it a bit to call that diagnostic accurate. The real user error is trying to initialize a static const double in the first place, not the details of what we're trying to initialize it with.

You're right that this code is invalid, but I think your average user who gets this error message might be mystified about what's wrong.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]