---
title: "uuid (C++) | Microsoft Docs"
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ms.date: "11/04/2016"
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f1_keywords: ["uuid", "uuid_cpp"]
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---

Microsoft Specific

The compiler attaches a GUID to a class or structure declared or defined (full COM object definitions only) with the uuid attribute.

  
__declspec( uuid("  
ComObjectGUID  
") ) declarator  

The uuid attribute takes a string as its argument. This string names a GUID in normal registry format with or without the { } delimiters. For example:

struct __declspec(uuid("00000000-0000-0000-c000-000000000046")) IUnknown;  
struct __declspec(uuid("{00020400-0000-0000-c000-000000000046}")) IDispatch;  

This attribute can be applied in a redeclaration. This allows the system headers to supply the definitions of interfaces such as IUnknown, and the redeclaration in some other header (such as COMDEF.H) to supply the GUID.

The keyword __uuidof can be applied to retrieve the constant GUID attached to a user-defined type.

END Microsoft Specific

__declspec
Keywords