Compiler Warning (level 1) C4929


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The latest version of this topic can be found at Compiler Warning (level 1) C4929.

file': typelibrary contains a union; ignoring the 'embedded_idl' qualifier

The embedded_idl attribute of #import could not be applied to the type library because a union is present in the type library. To resolve this warning, don't use embedded_idl.

The following sample defines a component.

// C4929a.cpp  
// compile with: /LD /link /TLBOUT:C4929a.tlb  
#include <objbase.h>  
[public, switch_type(short)] typedef union _TD_UNION_TYPE   {  
      float fM;  
      double dMN;  
      int x;  
[export, public] typedef struct _TDW_TYPE {  
   [switch_is(sU)] TD_UNION_TYPE w;  
      short sU;  
} TD_TYPE;  
[object, uuid("00000000-0000-0000-0000-000000000001")]  
__interface I {  
[coclass, uuid("00000000-0000-0000-0000-000000000002")]  
struct C : I {  
   HRESULT f(TD_TYPE*) { return 0; }  

The following sample generates C4929.

// C4929b.cpp  
// compile with: /c /W1  
#import "C4929a.tlb" embedded_idl   // C4929