http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56208
Bug #: 56208
Summary: sizeof sfinae fails to work
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: daniel.krueg...@googlemail.com
The following program becomes rejected when compiled with gcc 4.8.0 trunk using
the flags:
-Wall -pedantic
(with or without -std=c++11)
//--------------------------------
struct ostream {
ostream& operator<<(int);
};
struct sfinae_base {
typedef char one;
typedef char (&two)[2];
template<class T>
static T make();
template<unsigned> struct ok { typedef int type; };
template<class U, class T>
static one test(typename ok<sizeof(
make<U>() << make<T>()
)>::type);
template<class, class>
static two test(...);
};
template<class T>
struct is_printable : private sfinae_base
{
enum { value = sizeof(test<ostream&, T>(0)) == sizeof(one) };
};
typedef int ok[is_printable<int>::value ? 1 : -1];
int main() {}
//--------------------------------
"Compilation finished with errors:
source.cpp:31:49: error: size of array 'ok' is negative
typedef int ok[is_printable<int>::value ? 1 : -1];
^"
It worked with gcc 4.7.2 (also with Clang 3.2 or Intel-13), so this looks like
a regression to me. Operator<< is not the only one, I also noted problems with
other operators (such as binary plus).
