[Bug c++/37066] New: partial specialization of function depends on the order

["marc dot glisse at normalesup dot org" <gcc-bugzilla at gcc dot gnu dot org>]

In the following code, adapted from gmpxx, the output is HELLO2. If however I
change the order of the two partial specializations, the output becomes HELLO1.
At least one other compiler I tried outputs HELLO1 in both cases. I know that I
can remove the "template<>" and overload the function instead of partially
specializing it, but I would like to understand why the current code is
failing.


#include <iostream>

struct mpz_t{};

template <class T, class U>
class __gmp_expr{};

template <class T, class U>
void __gmp_set_expr(const __gmp_expr<T, U> &);

typedef __gmp_expr<mpz_t, mpz_t> mpz_class;

template <>
void __gmp_set_expr(const __gmp_expr<mpz_t, mpz_t> &expr)
{
    std::cerr << "HELLO1\n";
}

template <class T>
void __gmp_set_expr(const __gmp_expr<mpz_t, T> &expr)
{
    std::cerr << "HELLO2\n";
}

int main(){
    mpz_class a;
    mpz_t t;
    __gmp_set_expr(a);
}


-- 
           Summary: partial specialization of function depends on the order
           Product: gcc
           Version: 4.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: marc dot glisse at normalesup dot org
  GCC host triplet: i486-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37066