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 extern_ovl {
  81   extern "C" {
  82     __attribute__((overloadable))
  83     void ovl_decl(void); // expected-note {{previous}}
  84
  85     __attribute__((overloadable))
  86     int ovl_decl(int);
  87
  88     __attribute__((overloadable))
  89     int ovl_decl(void); // expected-error {{functions that differ only in their return type}}
  90   }
  91 }
  92
  93 namespace linkage {
  94   namespace redecl {
  95     extern "C" {
  96       static void linkage_redecl();
  97       static void linkage_redecl(int);
  98       void linkage_redecl(); // ok, still not extern "C"
  99       void linkage_redecl(int); // ok, still not extern "C"
 100       void linkage_redecl(float); // expected-note {{previous}}
 101       void linkage_redecl(double); // expected-error {{conflicting types}}
 102     }
 103   }
 104   namespace redecl_2 {
 105     extern "C" {
 106       void linkage_redecl_2(); // expected-note {{previous}}
 107       int linkage_redecl_2(int); // expected-error {{conflicting types}}
 108     }
 109   }
 110   namespace from_outer {
 111     void linkage_from_outer_1(); // expected-note {{previous}}
 112     void linkage_from_outer_2(); // expected-note {{previous}}
 113     extern "C" {
 114       void linkage_from_outer_1(int);
 115       void linkage_from_outer_1(); // expected-error {{different language linkage}}
 116       void linkage_from_outer_2(); // expected-error {{different language linkage}}
 117     }
 118   }
 119   namespace mixed {
 120     extern "C" {
 121       void linkage_mixed_1();
 122       static void linkage_mixed_1(int);
 123
 124       static void linkage_mixed_2(int);
 125       void linkage_mixed_2();
 126     }
 127   }
 128   namespace across_scopes {
 129     namespace X {
 130       extern "C" void linkage_across_scopes_f() {
 131         void linkage_across_scopes_g(); // expected-note {{previous}}
 132       }
 133     }
 134     namespace Y {
 135       extern "C" void linkage_across_scopes_g(int); // expected-error {{conflicting}}
 136     }
 137   }
 138 }
 139
 140 int lookup_in_global_f; // expected-note {{here}}
 141 namespace lookup_in_global {
 142   void lookup_in_global_f();
 143   void lookup_in_global_g();
 144   extern "C" {
 145     void lookup_in_global_f(int); // expected-error {{conflicts with declaration in global scope}}
 146     void lookup_in_global_g(int); // expected-note {{here}}
 147   }
 148 }
 149 int lookup_in_global_g; // expected-error {{conflicts with declaration with C language linkage}}
 150
 151 namespace N1 {
 152   extern "C" int different_kind_1; // expected-note {{here}}
 153   extern "C" void different_kind_2(); // expected-note {{here}}
 154 }
 155 namespace N2 {
 156   extern "C" void different_kind_1(); // expected-error {{different kind of symbol}}
 157   extern "C" int different_kind_2; // expected-error {{different kind of symbol}}
 158 }
 159
 160 // We allow all these even though the standard says they are ill-formed.
 161 extern "C" {
 162   struct stat {};   // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
 163   void stat(struct stat);
 164 }
 165 namespace X {
 166   extern "C" {
 167     void stat(struct ::stat);
 168   }
 169 }
 170 int stat(int *p);
 171 void global_fn_vs_extern_c_var_1();
 172 namespace X {
 173   extern "C" int global_fn_vs_extern_c_var_1;
 174   extern "C" int global_fn_vs_extern_c_var_2;
 175 }
 176 void global_fn_vs_extern_c_var_2();
 177 void global_fn_vs_extern_c_fn_1();
 178 namespace X {
 179   extern "C" int global_fn_vs_extern_c_fn_1(int);
 180   extern "C" int global_fn_vs_extern_c_fn_2(int);
 181 }
 182 void global_fn_vs_extern_c_fn_2();
 183 extern "C" void name_with_using_decl_1(int);
 184 namespace using_decl {
 185   void name_with_using_decl_1();
 186   void name_with_using_decl_2();
 187   void name_with_using_decl_3();
 188 }
 189 using using_decl::name_with_using_decl_1;
 190 using using_decl::name_with_using_decl_2;
 191 extern "C" void name_with_using_decl_2(int);
 192 extern "C" void name_with_using_decl_3(int);
 193 using using_decl::name_with_using_decl_3;
 194
 195 // We do not allow a global variable and an extern "C" function to have the same
 196 // name, because such entities may have the same mangled name.
 197 int global_var_vs_extern_c_fn_1; // expected-note {{here}}
 198 namespace X {
 199   extern "C" void global_var_vs_extern_c_fn_1(); // expected-error {{conflicts with declaration in global scope}}
 200   extern "C" void global_var_vs_extern_c_fn_2(); // expected-note {{here}}
 201 }
 202 int global_var_vs_extern_c_fn_2; // expected-error {{conflicts with declaration with C language linkage}}
 203 int global_var_vs_extern_c_var_1; // expected-note {{here}}
 204 namespace X {
 205   extern "C" double global_var_vs_extern_c_var_1; // expected-error {{conflicts with declaration in global scope}}
 206   extern "C" double global_var_vs_extern_c_var_2; // expected-note {{here}}
 207 }
 208 int global_var_vs_extern_c_var_2; // expected-error {{conflicts with declaration with C language linkage}}
 209
 210 template <class T> struct pr5065_n1 {};
 211 extern "C" {
 212   union pr5065_1 {}; // expected-warning{{empty union has size 0 in C, size 1 in C++}}
 213   struct pr5065_2 { int: 0; }; // expected-warning{{struct has size 0 in C, size 1 in C++}}
 214   struct pr5065_3 {}; // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
 215   struct pr5065_4 { // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
 216     struct Inner {}; // expected-warning{{empty struct has size 0 in C, size 1 in C++}}
 217   };
 218   // These should not warn
 219   class pr5065_n3 {};
 220   pr5065_n1<int> pr5065_v;
 221   struct pr5065_n4 { void m() {} };
 222   struct pr5065_n5 : public pr5065_3 {};
 223   struct pr5065_n6 : public virtual pr5065_3 {};
 224 }
 225 struct pr5065_n7 {};
 226
 227 namespace tag_hiding {
 228   namespace namespace_with_injected_name {
 229     class Boo {
 230       friend struct ExternCStruct1;
 231     };
 232     void ExternCStruct4(); // expected-note 2{{candidate}}
 233   }
 234
 235   class Baz {
 236     friend struct ExternCStruct2;
 237     friend void ExternCStruct3();
 238   };
 239
 240   using namespace namespace_with_injected_name;
 241
 242   extern "C" {
 243     struct ExternCStruct1;
 244     struct ExternCStruct2;
 245     struct ExternCStruct3;
 246     struct ExternCStruct4; // expected-note {{candidate}}
 247   }
 248   ExternCStruct1 *p1;
 249   ExternCStruct2 *p2;
 250   ExternCStruct3 *p3;
 251   ExternCStruct4 *p4; // expected-error {{ambiguous}}
 252
 253   extern "C" {
 254     struct ExternCStruct1;
 255     struct ExternCStruct2;
 256     struct ExternCStruct3;
 257     struct ExternCStruct4; // expected-note {{candidate}}
 258   }
 259   ExternCStruct1 *q1 = p1;
 260   ExternCStruct2 *q2 = p2;
 261   ExternCStruct3 *q3 = p3;
 262   ExternCStruct4 *q4 = p4; // expected-error {{ambiguous}}
 263 }
 264
 265 namespace PR35697 {
 266   typedef struct {} *ReturnStruct;
 267   extern "C" ReturnStruct PR35697_f();
 268   extern "C" ReturnStruct PR35697_v;
 269   ReturnStruct PR35697_f();
 270   ReturnStruct PR35697_v;
 271
 272   namespace {
 273     extern "C" ReturnStruct PR35697_f();
 274     extern "C" ReturnStruct PR35697_v;
 275     void q() {
 276       extern ReturnStruct PR35697_f();
 277       extern ReturnStruct PR35697_v;
 278     }
 279   }
 280 }
 281
 282 namespace PR46859 {
 283   extern "bogus" // expected-error {{unknown linkage language}}
 284     template<int> struct X {}; // expected-error {{templates can only be declared in namespace or class scope}}
 285 }