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      1 // RUN: %clang_cc1 -Wreturn-type -fsyntax-only -std=c++11 -verify %s
      2 
      3 class A {
      4 public:
      5   A(const A&);
      6 };
      7 
      8 struct S {
      9   int i;
     10   double d;
     11 
     12   virtual void B() {}
     13 };
     14 
     15 union U {
     16   struct {
     17     int i;
     18     virtual void B() {} // Can only do this in C++11
     19   } t;
     20 };
     21 
     22 struct S2 {
     23   int i;
     24   double d;
     25 };
     26 
     27 extern "C" U f3( void ); // expected-warning {{'f3' has C-linkage specified, but returns user-defined type 'U' which is incompatible with C}}
     28 extern "C" S f0(void); // expected-warning {{'f0' has C-linkage specified, but returns user-defined type 'S' which is incompatible with C}}
     29 extern "C" A f4( void ); // expected-warning {{'f4' has C-linkage specified, but returns user-defined type 'A' which is incompatible with C}}
     30 
     31 // These should all be fine
     32 extern "C" S2 f5( void );
     33 extern "C" void f2( A x );
     34 extern "C" void f6( S s );
     35 extern "C" void f7( U u );
     36 extern "C" double f8(void);
     37 extern "C" long long f11( void );
     38 extern "C" A *f10( void );
     39 
     40 extern "C" struct mypodstruct f12(); // expected-warning {{'f12' has C-linkage specified, but returns incomplete type 'struct mypodstruct' which could be incompatible with C}}
     41 
     42 namespace test2 {
     43   // FIXME: we should probably suppress the first warning as the second one
     44   // is more precise.
     45   // For now this tests that a second 'extern "C"' is not necessary to trigger
     46   // the warning.
     47   struct A;
     48   extern "C" A f(void); // expected-warning {{'f' has C-linkage specified, but returns incomplete type 'test2::A' which could be incompatible with C}}
     49   struct A {
     50     A(const A&);
     51   };
     52   A f(void);  // no warning. warning is already issued on first declaration.
     53 }
     54 
     55 namespace test3 {
     56   struct A {
     57     A(const A&);
     58   };
     59   extern "C" {
     60     // Don't warn for static functions.
     61     static A f(void);
     62   }
     63 }
     64 
     65 // rdar://13364028
     66 namespace rdar13364028 {
     67 class A {
     68 public:
     69     virtual int x();
     70 };
     71 
     72 extern "C" {
     73 #pragma clang diagnostic push
     74 #pragma clang diagnostic ignored "-Wreturn-type-c-linkage"
     75 A xyzzy();
     76 #pragma clang diagnostic pop
     77 A bbb(); // expected-warning {{'bbb' has C-linkage specified, but returns user-defined type 'rdar13364028::A' which is incompatible with C}}
     78 A ccc() { // expected-warning {{'ccc' has C-linkage specified, but returns user-defined type 'rdar13364028::A' which is incompatible with C}}
     79   return A();
     80 };
     81 }
     82 
     83 A xyzzy();
     84 
     85 A xyzzy()
     86 {
     87   return A();
     88 }
     89 
     90 A bbb()
     91 {
     92   return A();
     93 }
     94 
     95 A bbb();
     96 
     97 A ccc();
     98 }
     99