clang/test/CXX/temp/temp.pre/p6.cpp

   1 // RUN: %clang_cc1 -std=c++20 -verify %s
   2
   3 // Templates and partial and explicit specializations can't have C linkage.
   4 namespace extern_c_templates {
   5
   6 template<typename T> struct A {
   7   static int a;
   8   struct b;
   9   void c();
  10   enum class d;
  11
  12   template<typename U> static int e;
  13   template<typename U> struct f;
  14   template<typename U> void g();
  15 };
  16
  17 template<typename T> int B;
  18 template<typename T> void C();
  19
  20 extern "C" { // expected-note 1+{{begins here}}
  21   // templates
  22   template<typename T> struct A; // expected-error {{templates must have C++ linkage}}
  23   template<typename T> int B; // expected-error {{templates must have C++ linkage}}
  24   template<typename T> void C(); // expected-error {{templates must have C++ linkage}}
  25
  26   // non-template members of a template
  27   // FIXME: Should these really be valid?
  28   template<typename T> int A<T>::a;
  29   template<typename T> struct A<T>::b {};
  30   template<typename T> void A<T>::c() {}
  31   template<typename T> enum class A<T>::d {};
  32
  33   // templates
  34   template<typename T> template<typename U> int A<T>::e; // expected-error {{templates must have C++ linkage}}
  35   template<typename T> template<typename U> struct A<T>::f {}; // expected-error {{templates must have C++ linkage}}
  36   template<typename T> template<typename U> void A<T>::g() {} // expected-error {{templates must have C++ linkage}}
  37
  38   // partial specializations
  39   template<typename T> struct A<int*>; // expected-error {{templates must have C++ linkage}}
  40   template<typename T> int B<int*>; // expected-error {{templates must have C++ linkage}}
  41   template<typename T> template<typename U> int A<T>::e<U*>; // expected-error {{templates must have C++ linkage}}
  42   template<typename T> template<typename U> struct A<T>::f<U*> {}; // expected-error {{templates must have C++ linkage}}
  43
  44   // explicit specializations of templates
  45   template<> struct A<char> {}; // expected-error {{templates must have C++ linkage}}
  46   template<> int B<char>; // expected-error {{templates must have C++ linkage}}
  47   template<> void C<char>() {} // expected-error {{templates must have C++ linkage}}
  48
  49   // explicit specializations of members of a template
  50   template<> int A<int>::a; // expected-error {{templates must have C++ linkage}}
  51   template<> struct A<int>::b {}; // expected-error {{templates must have C++ linkage}}
  52   template<> void A<int>::c() {} // expected-error {{templates must have C++ linkage}}
  53   template<> enum class A<int>::d {}; // expected-error {{templates must have C++ linkage}}
  54
  55   // explicit specializations of member templates
  56   template<> template<typename U> int A<int>::e; // expected-error {{templates must have C++ linkage}}
  57   template<> template<typename U> struct A<int>::f {}; // expected-error {{templates must have C++ linkage}}
  58   template<> template<typename U> void A<int>::g() {} // expected-error {{templates must have C++ linkage}}
  59 }
  60
  61 // Provide valid definitions for the explicit instantiations below.
  62 // FIXME: Our recovery from the invalid definitions above isn't very good.
  63 template<typename T> template<typename U> int A<T>::e;
  64 template<typename T> template<typename U> struct A<T>::f {};
  65 template<typename T> template<typename U> void A<T>::g() {}
  66
  67 extern "C" {
  68   // explicit instantiations
  69   // FIXME: Should these really be valid?
  70   template struct A<double>;
  71   template int A<float>::a;
  72   template struct A<float>::b;
  73   template void A<float>::c();
  74   template int A<float>::e<float>;
  75   template struct A<float>::f<float>;
  76   template void A<float>::g<float>();
  77 }
  78
  79 }