The fact that std::pair has operator>= defined in namespace std "hides" oprator>= defined in namespace std::rel_ops, for all classes.
operator>= for pairs is defined in <bits/stl_pair.h>, and it is in namespace std; This only happens when " >= " is used from std, as in the case of "greater_equal". I use >= as an example, the same happens for (<=, >, .....) I've tested this behavior with gcc 4.4.0 (on Fedora 11), gcc 4.3.X and 3.4.X from cygwin. This small c++ program fails with (compiled as g++ -c foo.cpp) (If I add -Wall, it reports about ok and bad not being used). In file included from /usr/lib/gcc/i586-redhat-linux/4.4.0/../../../../include/c++/4.4.0/functional:51, from foo.cpp:3: /usr/lib/gcc/i586-redhat-linux/4.4.0/../../../../include/c++/4.4.0/bits/stl_function.h: In member function bool std::greater_equal<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = A]: foo.cpp:20: instantiated from here /usr/lib/gcc/i586-redhat-linux/4.4.0/../../../../include/c++/4.4.0/bits/stl_function.h:239: error: no match for operator>= in __x >= __y #include <utility> #include <functional> using namespace std; using namespace std::rel_ops; struct A { bool operator<(const A &) const; }; void foo1() { bool ok = A() >= A(); // just to check rel_ops is actually included } void foo2() { greater_equal<A> ge; bool bad = ge(A(), A()); } The only way to make it compile so far is to add namespace std { namespace rel_ops { } using namespace rel_ops; } so that rel_ops::operator>= is found by "greater_equal". If I only add using namespace std::rel_ops; in my C++ source code, it is not enough, since (I think) gcc chooses (while parsing greater_equal) the operator>= defined in std (the only one available at that time), and when an other one is added later (from rel_ops) it is too late. Alternatively, if I move operator>= for pair into std::rel_ops everything works. I am not sure where is the root of the problem, but my thoughts are 1) why do we need an operator >= for pair? is it not enough the one for all <T>? 2) why is operator>= for pair in std and not in std::rel_ops? 3) is gcc correct in ignoring operator>= from rel_ops? -- Summary: STL: operator>= for pair "hides" general operator>= from std::rel_ops Product: gcc Version: 4.4.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: mariofutire at googlemail dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40804