Using a trunk gcc:

$ cat test.cc
template<typename _Ex>
void
__throw_with_nested(const _Ex&, const int* = 0)
    __attribute__ ((__noreturn__));

template<typename _Ex>
inline void
__throw_with_nested(const _Ex& __ex, const int* = 0)
{ throw __ex; }

void foo() {
  __throw_with_nested(3);
}
$ g++  -c test.cc
$

However, if I make them non-templates:

$ cat test.cc
void
__throw_with_nested(const int&, const int* = 0)
    __attribute__ ((__noreturn__));

inline void
__throw_with_nested(const int& __ex, const int* = 0)
{ throw __ex; }

void foo() {
  __throw_with_nested(3);
}
$ g++  -c test.cc
test.cc: In function ‘void __throw_with_nested(const int&, const int*)’:
test.cc:6:52: error: default argument given for parameter 2 of ‘void __throw_with_nested(const int&, const int*)’ [-fpermissive]
test.cc:2:1: error: after previous specification in ‘void __throw_with_nested(const int&, const int*)’ [-fpermissive]
$