The following code contains a test template is_class which tries to determine,
if the given argument is a class. Unlike other implementations it should not
return true if the argument is a union. I have used the 'substitution failure
is not an error' principle but g++ V3.3.5 (Debian 1:3.3.5-12) (i486-linux)
fails with an error though it has a default function available. Since I do not
have the standard I can't declare this a bug.
---- bug.c
cusing namespace std;
#include <iostream>
template<typename _T>
struct is_class
{
typedef char no;
struct yes { char c[2]; };
template<typename _U>
struct c: _U
{
c(int);
};
template<typename _U> static no test (...);
template<typename _U> static yes test(c<_U>);
static const bool v = (sizeof (test<_T>(0))==sizeof(yes));
};
union u { int i; double f; };
struct c {};
int main (void)
{
cout << "union:" << is_class<u>::v << endl;
cout << "class:" << is_class<c>::v << endl;
cout << "int:" << is_class<int>::v << endl;
return 0;
};
--
Summary: Possible bug
Product: gcc
Version: 3.4.3
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: sven at clio dot in-berlin dot de
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i486-linux
GCC host triplet: i486-linux
GCC target triplet: i486-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21510
