// N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf 
#define msg "p212.cpp(98) 8.3.6 Default arguments [dcl.fct.default]"

#include <iostream>

void point(int = 3, int = 4);

point(1,2); point(1); point();

void g(int = 0, ...); // OK, ellipsis is not a parameter so it can follow
// a parameter with a default argument
void f(int, int);
void f(int, int = 7);
void h() {
  f(3); // OK, calls f(3, 7)
  void f(int = 1, int); // error: does not use default
  // from surrounding scope
}
void m() {
  void f(int, int); // has no defaults
  f(4); // error: wrong number of arguments
  void f(int, int = 5); // OK
  f(4); // OK, calls f(4, 5);
  void f(int, int = 5); // error: cannot redefine, even to
  // same value
}
void n() {
  f(6); // OK, calls f(6, 7)
}

int a = 1;
int f(int);
int g(int x = f(a)); // default argument: f(::a)
void h() {
  a = 2;
  {
    int a = 3;
    g(); // g(f(::a))
  }
}

class C {
  void f(int i = 3);
  void g(int i, int j = 99);
};
void C::f(int i = 3) { // error: default argument already
} // specified in class scope
  void C::g(int i = 88, int j) { // in this   translation unit,
} // C::

void f() {
  int i;
  extern void g(int x = i); // error
  extern void h(int x = sizeof(i)); // OK
  // ...
}

class A {
  void f(A* p = this) { } // error
};

int a;
int f(int a, int b = a); // error: parameter a
// used as default argument
typedef int I;
int g(float I, int b = I(2)); // error: parameter I found
int h(int a, int b = sizeof(a)); // OK, unevaluated operand
int b;
class X {
  int a;
  int mem1(int i = a); // error: non-static member a
  // used as default argument
  int mem2(int i = b); // OK; use X::b
  static int b;
};

int f(int = 0);
void h() {
  int j = f(1);
  int k = f(); // OK, means f(0)
}
int (*p1)(int) = &f;
int (*p2)() = &f; // error: type mismatch

struct A {
  virtual void f(int a = 7);
};
struct B : public A {
  void f(int a);
};
void m() {
  B* pb = new B;
  A* pa = pb;
  pa->f(); // OK, calls pa->B::f(7)
  pb->f(); // error: wrong number of arguments   for B::f()
}

int main(){
  m();
  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

$ ./cppgl17.sh p212
$ clang++ p212.cpp
p212.cpp:9:1: error: C++ requires a type specifier for all declarations
point(1,2); point(1); point();
^
p212.cpp:9:13: error: C++ requires a type specifier for all declarations
point(1,2); point(1); point();
            ^
p212.cpp:9:23: error: C++ requires a type specifier for all declarations
point(1,2); point(1); point();
                      ^
p212.cpp:17:22: error: missing default argument on parameter
  void f(int = 1, int); // error: does not use default
                     ^
p212.cpp:22:3: error: too few arguments to function call, expected 2, have 1; did you mean '::f'?
  f(4); // error: wrong number of arguments
  ^
  ::f
p212.cpp:14:6: note: '::f' declared here
void f(int, int = 7);
     ^
p212.cpp:25:19: error: redefinition of default argument
  void f(int, int = 5); // error: cannot redefine, even to
                  ^ ~
p212.cpp:23:19: note: previous definition is here
  void f(int, int = 5); // OK
                  ^ ~
p212.cpp:34:15: error: call to 'f' is ambiguous
int g(int x = f(a)); // default argument: f(::a)
              ^
p212.cpp:14:6: note: candidate function
void f(int, int = 7);
     ^
p212.cpp:33:5: note: candidate function
int f(int);
    ^
p212.cpp:35:6: error: redefinition of 'h'
void h() {
     ^
p212.cpp:15:6: note: previous definition is here
void h() {
     ^
p212.cpp:47:15: error: redefinition of default argument
void C::f(int i = 3) { // error: default argument already
              ^   ~
p212.cpp:44:14: note: previous definition is here
  void f(int i = 3);
             ^   ~
p212.cpp:54:25: error: default argument references local variable 'i' of enclosing function
  extern void g(int x = i); // error
                        ^
p212.cpp:55:32: error: default argument references local variable 'i' of enclosing function
  extern void h(int x = sizeof(i)); // OK
                        ~~~~~~~^~
p212.cpp:60:17: error: invalid use of 'this' outside of a non-static member function
  void f(A* p = this) { } // error
                ^
p212.cpp:63:5: error: redefinition of 'a'
int a;
    ^
p212.cpp:32:5: note: previous definition is here
int a = 1;
    ^
p212.cpp:64:22: error: default argument references parameter 'a'
int f(int a, int b = a); // error: parameter a
                     ^
p212.cpp:67:25: error: called object type 'float' is not a function or function pointer
int g(float I, int b = I(2)); // error: parameter I found
                       ~^
p212.cpp:68:29: error: default argument references parameter 'a'
int h(int a, int b = sizeof(a)); // OK, unevaluated operand
                     ~~~~~~~^~
p212.cpp:72:20: error: invalid use of non-static data member 'a'
  int mem1(int i = a); // error: non-static member a
                   ^
p212.cpp:80:11: error: call to 'f' is ambiguous
  int j = f(1);
          ^
p212.cpp:14:6: note: candidate function
void f(int, int = 7);
     ^
p212.cpp:78:5: note: candidate function
int f(int = 0);
    ^
p212.cpp:81:11: error: call to 'f' is ambiguous
  int k = f(); // OK, means f(0)
          ^
p212.cpp:52:6: note: candidate function
void f() {
     ^
p212.cpp:78:5: note: candidate function
int f(int = 0);
    ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

$ g++-7 p212.cpp
p212.cpp:9:6: error: expected constructor, destructor, or type conversion before '(' token
 point(1,2); point(1); point();
      ^
p212.cpp:9:18: error: expected constructor, destructor, or type conversion before '(' token
 point(1,2); point(1); point();
                  ^
p212.cpp:9:30: error: expected constructor, destructor, or type conversion before ';' token
 point(1,2); point(1); point();
                              ^
p212.cpp: In function 'void h()':
p212.cpp:17:8: error: default argument missing for parameter 2 of 'void f(int, int)'
   void f(int = 1, int); // error: does not use default
        ^
p212.cpp: In function 'void m()':
p212.cpp:22:6: error: too few arguments to function 'void f(int, int)'
   f(4); // error: wrong number of arguments
      ^
p212.cpp:21:8: note: declared here
   void f(int, int); // has no defaults
        ^
p212.cpp:25:22: error: default argument given for parameter 2 of 'void f(int, int)' [-fpermissive]
   void f(int, int = 5); // error: cannot redefine, even to
                      ^
p212.cpp:23:8: note: previous specification in 'void f(int, int)' here
   void f(int, int = 5); // OK
        ^
p212.cpp: At global scope:
p212.cpp:34:18: error: call of overloaded 'f(int&)' is ambiguous
 int g(int x = f(a)); // default argument: f(::a)
                  ^
p212.cpp:14:6: note: candidate: void f(int, int)
 void f(int, int = 7);
      ^
p212.cpp:33:5: note: candidate: int f(int)
 int f(int);
     ^
p212.cpp: In function 'void h()':
p212.cpp:35:6: error: redefinition of 'void h()'
 void h() {
      ^
p212.cpp:15:6: note: 'void h()' previously defined here
 void h() {
      ^
p212.cpp:39:7: error: call of overloaded 'g()' is ambiguous
     g(); // g(f(::a))
       ^
p212.cpp:11:6: note: candidate: void g(int, ...)
 void g(int = 0, ...); // OK, ellipsis is not a parameter so it can follow
      ^
p212.cpp:34:5: note: candidate: int g(int)
 int g(int x = f(a)); // default argument: f(::a)
     ^
p212.cpp: At global scope:
p212.cpp:47:20: error: default argument given for parameter 1 of 'void C::f(int)' [-fpermissive]
 void C::f(int i = 3) { // error: default argument already
                    ^
p212.cpp:44:8: note: previous specification in 'void C::f(int)' here
   void f(int i = 3);
        ^
p212.cpp: In function 'void f()':
p212.cpp:54:25: error: local variable 'i' may not appear in this context
   extern void g(int x = i); // error
                         ^
p212.cpp:55:32: error: local variable 'i' may not appear in this context
   extern void h(int x = sizeof(i)); // OK
                                ^
p212.cpp: At global scope:
p212.cpp:60:17: error: 'this' may not be used in this context
   void f(A* p = this) { } // error
                 ^~~~
p212.cpp:63:5: error: redefinition of 'int a'
 int a;
     ^
p212.cpp:32:5: note: 'int a' previously defined here
 int a = 1;
     ^
p212.cpp:64:22: error: local variable 'a' may not appear in this context
 int f(int a, int b = a); // error: parameter a
                      ^
p212.cpp:64:5: error: ambiguating new declaration of 'int f(int, int)'
 int f(int a, int b = a); // error: parameter a
     ^
p212.cpp:14:6: note: old declaration 'void f(int, int)'
 void f(int, int = 7);
      ^
p212.cpp:67:24: error: local variable 'I' may not appear in this context
 int g(float I, int b = I(2)); // error: parameter I found
                        ^
p212.cpp:68:29: error: local variable 'a' may not appear in this context
 int h(int a, int b = sizeof(a)); // OK, unevaluated operand
                             ^
p212.cpp:72:20: error: invalid use of non-static data member 'X::a'
   int mem1(int i = a); // error: non-static member a
                    ^
p212.cpp:71:7: note: declared here
   int a;
       ^
p212.cpp: In function 'void h()':
p212.cpp:79:6: error: redefinition of 'void h()'
 void h() {
      ^
p212.cpp:15:6: note: 'void h()' previously defined here
 void h() {
      ^
p212.cpp:80:14: error: call of overloaded 'f(int)' is ambiguous
   int j = f(1);
              ^
p212.cpp:14:6: note: candidate: void f(int, int)
 void f(int, int = 7);
      ^
p212.cpp:78:5: note: candidate: int f(int)
 int f(int = 0);
     ^
p212.cpp:81:13: error: call of overloaded 'f()' is ambiguous
   int k = f(); // OK, means f(0)
             ^
p212.cpp:78:5: note: candidate: int f(int)
 int f(int = 0);
     ^
p212.cpp:52:6: note: candidate: void f()
 void f() {
      ^
p212.cpp: At global scope:
p212.cpp:84:16: error: no matches converting function 'f' to type 'int (*)()'
 int (*p2)() = &f; // error: type mismatch
                ^
p212.cpp:52:6: note: candidates are: void f()
 void f() {
      ^
p212.cpp:78:5: note:                 int f(int)
 int f(int = 0);
     ^
p212.cpp:14:6: note:                 void f(int, int)
 void f(int, int = 7);
      ^
p212.cpp:86:8: error: redefinition of 'struct A'
 struct A {
        ^
p212.cpp:59:7: note: previous definition of 'struct A'
 class A {
       ^
p212.cpp: In function 'void m()':
p212.cpp:92:6: error: redefinition of 'void m()'
 void m() {
      ^
p212.cpp:20:6: note: 'void m()' previously defined here
 void m() {
      ^
p212.cpp:95:9: error: 'void A::f(A*)' is private within this context
   pa->f(); // OK, calls pa->B::f(7)
         ^
p212.cpp:60:8: note: declared private here
   void f(A* p = this) { } // error
        ^
p212.cpp:95:9: error: call to 'void A::f(A*)' uses the default argument for parameter 1, which is not yet defined
   pa->f(); // OK, calls pa->B::f(7)
         ^
p212.cpp:96:9: error: no matching function for call to 'B::f()'
   pb->f(); // error: wrong number of arguments   for B::f()
         ^
p212.cpp:90:8: note: candidate: void B::f(int)
   void f(int a);
        ^
p212.cpp:90:8: note:   candidate expects 1 argument, 0 provided