CONFIGRET返回类型是什么意思？

Question

I was taking a look at the PnP Configuration Manager functions and saw that each begins with these three macros:

CMAPI CONFIGRET WINAPI

I had to dig inside CfgMgr32.h to find CMAPI , which is defined as:

#if !defined (_CFGMGR32_)
#define CMAPI     DECLSPEC_IMPORT
#else
#define CMAPI
#endif

According to Tim Roberts' article on DLL's in Kernel Mode , this allows functions with CMAPI to be either loaded at run-time or link-time. And we already know that WINAPI is just a macro for a calling convention .

But what about CONFIGRET ? From CfgMgr32.h , it is defined as:

//
// Standardized Return Value data type
//
typedef _Return_type_success_(return == 0) DWORD        RETURN_TYPE;
typedef RETURN_TYPE  CONFIGRET;

I've never seen this before, what does this mean? What is the return type of these functions?

Answer 1

The underlying data type for CONFIGRET is a DWORD , as defined in CfgMgr32.h :

//
// Standardized Return Value data type
//
typedef _Return_type_success_(return == 0) DWORD        RETURN_TYPE;
typedef RETURN_TYPE  CONFIGRET;

CONFIGRET is an alias for RETURN_TYPE , and RETURN_TYPE an alias for a DWORD with additional semantic information attached by means of SAL annotations (SAL annotations are used by static code analyzers).

Annotating Function Behavior contains detailed information on this particular annotation:

_Return_type_success_(expr)

May be applied to a typedef. Indicates that all functions that return that type and do not explicitly have _Success_ are annotated as if they had _Success_(expr) . _Return_type_success_ cannot be used on a function or a function pointer typedef.

---

The CMAPI preprocessor symbol defined in CfgMgr32.h as

#if !defined (_CFGMGR32_)
#define CMAPI     DECLSPEC_IMPORT
#else
#define CMAPI
#endif

serves a different purpose, than what you proposed: It allows the same header file to be used for the consumer and producer of the library. The producer defines the _CFGMGR32_ preprocessor symbol, and provides the function definitions. The consumer doesn't define the _CFGMGR32_ preprocessor symbol, and CMAPI expands to an import specifier ( __declspec(dllimport) , defined in ntdef.h ). This is used for Load-Time Dynamic Linking (vs. Run-Time Dynamic Linking ). It is not used for static linking at all.