clang/test/SemaCXX/extern-c.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -verify %s
   2
   3 namespace test1 {
   4   extern "C" {
   5     void test1_f() {
   6       void test1_g(int);
   7     }
   8   }
   9 }
  10 int test1_g(int);
  11
  12 namespace test2 {
  13   extern "C" {
  14     void test2_f() {
  15       extern int test2_x; // expected-note {{declared with C language linkage here}}
  16     }
  17   }
  18 }
  19 float test2_x; // expected-error {{declaration of 'test2_x' in global scope conflicts with declaration with C language linkage}}
  20
  21 namespace test3 {
  22   extern "C" {
  23     void test3_f() {
  24       extern int test3_b; // expected-note {{previous declaration is here}}
  25     }
  26   }
  27   extern "C" {
  28     float test3_b; // expected-error {{redefinition of 'test3_b' with a different type: 'float' vs 'int'}}
  29   }
  30 }
  31
  32 namespace N {
  33   extern "C" {
  34     void test4_f() {
  35       extern int test4_b; // expected-note {{declared with C language linkage here}}
  36     }
  37   }
  38 }
  39 static float test4_b; // expected-error {{declaration of 'test4_b' in global scope conflicts with declaration with C language linkage}}
  40
  41 extern "C" {
  42   void test4c_f() {
  43     extern int test4_c; // expected-note {{previous}}
  44   }
  45 }
  46 static float test4_c; // expected-error {{redefinition of 'test4_c' with a different type: 'float' vs 'int'}}
  47
  48 namespace N {
  49   extern "C" {
  50     void test5_f() {
  51       extern int test5_b; // expected-note {{declared with C language linkage here}}
  52     }
  53   }
  54 }
  55 extern "C" {
  56   static float test5_b; // expected-error {{declaration of 'test5_b' in global scope conflicts with declaration with C language linkage}}
  57 }
  58
  59 extern "C" {
  60   void test5c_f() {
  61     extern int test5_c; // expected-note {{previous}}
  62   }
  63 }
  64 extern "C" {
  65   static float test5_c; // expected-error {{redefinition of 'test5_c' with a different type: 'float' vs 'int'}}
  66 }
  67
  68 extern "C" {
  69   void f() {
  70     extern int test6_b;
  71   }
  72 }
  73 namespace foo {
  74   extern "C" {
  75     static float test6_b;
  76     extern float test6_b;
  77   }
  78 }
  79
  80 namespace linkage {
  81   namespace redecl {
  82     extern "C" {
  83       static void linkage_redecl();
  84       static void linkage_redecl(int);
  85       void linkage_redecl(); // ok, still not extern "C"
  86       void linkage_redecl(int); // ok, still not extern "C"
  87       void linkage_redecl(float); // expected-note {{previous}}
  88       void linkage_redecl(double); // expected-error {{conflicting types}}
  89     }
  90   }
  91   namespace from_outer {
  92     void linkage_from_outer_1(); // expected-note {{previous}}
  93     void linkage_from_outer_2(); // expected-note {{previous}}
  94     extern "C" {
  95       void linkage_from_outer_1(int);
  96       void linkage_from_outer_1(); // expected-error {{different language linkage}}
  97       void linkage_from_outer_2(); // expected-error {{different language linkage}}
  98     }
  99   }
 100   namespace mixed {
 101     extern "C" {
 102       void linkage_mixed_1();
 103       static void linkage_mixed_1(int);
 104
 105       static void linkage_mixed_2(int);
 106       void linkage_mixed_2();
 107     }
 108   }
 109   namespace across_scopes {
 110     namespace X {
 111       extern "C" void linkage_across_scopes_f() {
 112         void linkage_across_scopes_g(); // expected-note {{previous}}
 113       }
 114     }
 115     namespace Y {
 116       extern "C" void linkage_across_scopes_g(int); // expected-error {{conflicting}}
 117     }
 118   }
 119 }
 120
 121 int lookup_in_global_f; // expected-note {{here}}
 122 namespace lookup_in_global {
 123   void lookup_in_global_f();
 124   void lookup_in_global_g();
 125   extern "C" {
 126     void lookup_in_global_f(int); // expected-error {{conflicts with declaration in global scope}}
 127     void lookup_in_global_g(int); // expected-note {{here}}
 128   }
 129 }
 130 int lookup_in_global_g; // expected-error {{conflicts with declaration with C language linkage}}
 131
 132 namespace N1 {
 133   extern "C" int different_kind_1; // expected-note {{here}}
 134   extern "C" void different_kind_2(); // expected-note {{here}}
 135 }
 136 namespace N2 {
 137   extern "C" void different_kind_1(); // expected-error {{different kind of symbol}}
 138   extern "C" int different_kind_2; // expected-error {{different kind of symbol}}
 139 }
 140
 141 // We allow all these even though the standard says they are ill-formed.
 142 extern "C" {
 143   struct stat {};   // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
 144   void stat(struct stat);
 145 }
 146 namespace X {
 147   extern "C" {
 148     void stat(struct ::stat);
 149   }
 150 }
 151 int stat(int *p);
 152 void global_fn_vs_extern_c_var_1();
 153 namespace X {
 154   extern "C" int global_fn_vs_extern_c_var_1;
 155   extern "C" int global_fn_vs_extern_c_var_2;
 156 }
 157 void global_fn_vs_extern_c_var_2();
 158 void global_fn_vs_extern_c_fn_1();
 159 namespace X {
 160   extern "C" int global_fn_vs_extern_c_fn_1(int);
 161   extern "C" int global_fn_vs_extern_c_fn_2(int);
 162 }
 163 void global_fn_vs_extern_c_fn_2();
 164 extern "C" void name_with_using_decl_1(int);
 165 namespace using_decl {
 166   void name_with_using_decl_1();
 167   void name_with_using_decl_2();
 168   void name_with_using_decl_3();
 169 }
 170 using using_decl::name_with_using_decl_1;
 171 using using_decl::name_with_using_decl_2;
 172 extern "C" void name_with_using_decl_2(int);
 173 extern "C" void name_with_using_decl_3(int);
 174 using using_decl::name_with_using_decl_3;
 175
 176 // We do not allow a global variable and an extern "C" function to have the same
 177 // name, because such entities may have the same mangled name.
 178 int global_var_vs_extern_c_fn_1; // expected-note {{here}}
 179 namespace X {
 180   extern "C" void global_var_vs_extern_c_fn_1(); // expected-error {{conflicts with declaration in global scope}}
 181   extern "C" void global_var_vs_extern_c_fn_2(); // expected-note {{here}}
 182 }
 183 int global_var_vs_extern_c_fn_2; // expected-error {{conflicts with declaration with C language linkage}}
 184 int global_var_vs_extern_c_var_1; // expected-note {{here}}
 185 namespace X {
 186   extern "C" double global_var_vs_extern_c_var_1; // expected-error {{conflicts with declaration in global scope}}
 187   extern "C" double global_var_vs_extern_c_var_2; // expected-note {{here}}
 188 }
 189 int global_var_vs_extern_c_var_2; // expected-error {{conflicts with declaration with C language linkage}}
 190
 191 template <class T> struct pr5065_n1 {};
 192 extern "C" {
 193   union pr5065_1 {}; // expected-warning{{empty union has size 0 in C, size 1 in C++}}
 194   struct pr5065_2 { int: 0; }; // expected-warning{{struct has size 0 in C, size 1 in C++}}
 195   struct pr5065_3 {}; // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
 196   struct pr5065_4 { // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
 197     struct Inner {}; // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
 198   };
 199   // These should not warn
 200   class pr5065_n3 {};
 201   pr5065_n1<int> pr5065_v;
 202   struct pr5065_n4 { void m() {} };
 203   struct pr5065_n5 : public pr5065_3 {};
 204   struct pr5065_n6 : public virtual pr5065_3 {};
 205 }
 206 struct pr5065_n7 {};
 207
 208 namespace tag_hiding {
 209   namespace namespace_with_injected_name {
 210     class Boo {
 211       friend struct ExternCStruct1;
 212     };
 213     void ExternCStruct4(); // expected-note 2{{candidate}}
 214   }
 215
 216   class Baz {
 217     friend struct ExternCStruct2;
 218     friend void ExternCStruct3();
 219   };
 220
 221   using namespace namespace_with_injected_name;
 222
 223   extern "C" {
 224     struct ExternCStruct1;
 225     struct ExternCStruct2;
 226     struct ExternCStruct3;
 227     struct ExternCStruct4; // expected-note {{candidate}}
 228   }
 229   ExternCStruct1 *p1;
 230   ExternCStruct2 *p2;
 231   ExternCStruct3 *p3;
 232   ExternCStruct4 *p4; // expected-error {{ambiguous}}
 233
 234   extern "C" {
 235     struct ExternCStruct1;
 236     struct ExternCStruct2;
 237     struct ExternCStruct3;
 238     struct ExternCStruct4; // expected-note {{candidate}}
 239   }
 240   ExternCStruct1 *q1 = p1;
 241   ExternCStruct2 *q2 = p2;
 242   ExternCStruct3 *q3 = p3;
 243   ExternCStruct4 *q4 = p4; // expected-error {{ambiguous}}
 244 }
 245
 246 namespace PR35697 {
 247   typedef struct {} *ReturnStruct;
 248   extern "C" ReturnStruct PR35697_f();
 249   extern "C" ReturnStruct PR35697_v;
 250   ReturnStruct PR35697_f();
 251   ReturnStruct PR35697_v;
 252
 253   namespace {
 254     extern "C" ReturnStruct PR35697_f();
 255     extern "C" ReturnStruct PR35697_v;
 256     void q() {
 257       extern ReturnStruct PR35697_f();
 258       extern ReturnStruct PR35697_v;
 259     }
 260   }
 261 }
 262
 263 namespace PR46859 {
 264   extern "bogus" // expected-error {{unknown linkage language}}
 265     template<int> struct X {}; // expected-error {{templates can only be declared in namespace or class scope}}
 266 }