clang/test/CXX/basic/basic.link/p6.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++1y %s
   2
   3 // expected-no-diagnostics
   4
   5 // C++11 [basic.link]p6:
   6 //   The name of a function declared in block scope and the name
   7 //   of a variable declared by a block scope extern declaration
   8 //   have linkage. If there is a visible declaration of an entity
   9 //   with linkage having the same name and type, ignoring entities
  10 //   declared outside the innermost enclosing namespace scope, the
  11 //   block scope declaration declares that same entity and
  12 //   receives the linkage of the previous declaration.
  13
  14 extern int same_entity;
  15 constexpr int *get1() {
  16   int same_entity = 0; // not the same entity
  17   {
  18     extern int same_entity;
  19     return &same_entity;
  20   }
  21 }
  22 static_assert(get1() == &same_entity, "failed to find previous decl");
  23
  24 static int same_entity_2[3];
  25 constexpr int *get2() {
  26   // This is a redeclaration of the same entity, even though it doesn't
  27   // inherit the type of the prior declaration.
  28   extern int same_entity_2[];
  29   return same_entity_2;
  30 }
  31 static_assert(get2() == same_entity_2, "failed to find previous decl");
  32
  33 static int different_entities;
  34 constexpr int *get3() {
  35   int different_entities = 0;
  36   {
  37     // FIXME: This is not a redeclaration of the prior entity, because
  38     // it is not visible here. Under DR426, this is ill-formed, and without
  39     // it, the static_assert below should fail.
  40     extern int different_entities;
  41     return &different_entities;
  42   }
  43 }
  44 static_assert(get3() == &different_entities, "failed to find previous decl");