// { dg-do compile }// Copyright 2005 Free Software Foundation// by Alexandre Oliva <aoliva@redhat.com>// based on https://bugzilla.redhat.com/beta/show_bug.cgi?id=149098// Per the ISO C++ 90 Standard, using declarations before of after a// declaration of the same function name and prototype should be// errors (7.3.3/11).  However, DR 101's resolution recommends// accepting such duplicates if they denote the same function, which// means extern "C" declarations are supposed to match and be// accepted.// This test makes sure we reject or accept regular and using// declarations regardless of order as appropriate, and that having// built-in declarations or overloads doesn't affet the outcome.namespace std {  extern "C" void exit (int) throw (); // these are built-in (extern "C")  extern "C" void *malloc (__SIZE_TYPE__) throw () __attribute__((malloc));  void abort (void) throw (); // these aren't  void _exit (int) throw (); // { dg-error "std::_exit" }  extern "C" void c1 (void) throw ();  void C1 (void) throw (); // { dg-error "std::C1" }  extern "C" void c2 (void) throw ();  void C2 (void) throw ();  extern "C" void c3 (void) throw ();  void C3 (void) throw (); // { dg-error "std::C3" }}namespace other {  extern "C" void c3 (void) throw ();  void C3 (void) throw (); // { dg-error "other::C3" }}using std::exit;using std::_exit;using std::c1;using std::C1;  extern "C" void exit (int) throw ();  extern "C" void *malloc (__SIZE_TYPE__) throw () __attribute__((malloc));  void abort (void) throw ();  void _exit (int) throw (); // { dg-error "conflicts|void _exit" }  extern "C" void c1 (void) throw ();  void C1 (void) throw (); // { dg-error "conflicts|void C1" }  extern "C" void c2 (void) throw ();  void C2 (void) throw ();  int C3 (int) throw ();using std::malloc;using std::abort; // { dg-error "already declared" }using std::c2;using std::C2; // { dg-error "already declared" }using std::c3; using other::c3;using std::C3; using other::C3;  long C3 (long) throw ();int main () {  malloc (0);  exit (0);  _exit (0); // { dg-error "ambiguous" }  abort ();  c1 ();  C1 (); // { dg-error "ambiguous" }  c2 ();  C2 (); // one might expect an ambiguous call error here as well, but	 // we don't add the using decl if we find it to be in error.  c3 ();  C3 (); // { dg-error "ambiguous" }  C3 (0);  C3 (0l);}