__stdcall with boost::function
I'm trying to pass a member function pointer around to the Windows Service Control Manager through Windpws API functions, but I think I'm having troubles with the __stdcall convention. I'm using MSVC 7.1.3088. For brevity I've left out information, but I think this is enough to go on: __ExampleClass.h__ class ExampleClass { protected: void Setup( void ); void __stdcall ServiceMain( DWORD dwArgc, LPSTR *lpszArgv ); LPSERVICE_MAIN_FUNCTION m_fServiceMain; }; __ExampleClass.cpp__ void ExampleClass::Setup( void ) { boost::function<void ( DWORD, LPSTR * )> f2 = boost::bind( boost::mem_fn( &ExampleClass::ServiceMain ), this, _1, _2 ); m_fServiceMain = f2.target<void ( DWORD, LPSTR * )>( ); SERVICE_TABLE_ENTRY dispatchTable[ ] = { { const_cast<char *>( g_sAPP_NAME.c_str( ) ), m_fServiceMain }, { 0, 0 } }; StartServiceCtrlDispatcher( dispatchTable ); } void __stdcall ExampleClass::ServiceMain( DWORD dwArgc, LPSTR *lpszArgv ) { } The error I receive concerns the line m_fServiceMain = f2.target<void ( DWORD, LPSTR * )>( ); error C2440: '=' : cannot convert from 'void (__cdecl *)(DWORD,LPSTR * )' to 'LPSERVICE_MAIN_FUNCTIONA' This conversion requires a reinterpret_cast, a C-style cast or function-style cast LPSERVICE_MAIN_FUNCTIONA is defined in "winsvc.h" and is: typedef VOID (WINAPI *LPSERVICE_MAIN_FUNCTIONA)( DWORD dwNumServicesArgs, LPSTR *lpServiceArgVectors ); Any help or insight would be much appreciated. -Jason
Olenhouse, Jason wrote:
I'm trying to pass a member function pointer around to the Windows Service Control Manager through Windpws API functions, but I think I'm having troubles with the __stdcall convention. <snip>
No, the problem is passing a member function pointer. A member function pointer is not type-compatible with a function pointer with the same parameter types, regardless of whether they have the same calling convention. ServiceMain has to be a static member or free function. If you really need to pass your own argument(s) to it then use a static variable or TLS slot. Ben.
On Mar 10, 2005, at 12:16 PM, Olenhouse, Jason wrote:
I'm trying to pass a member function pointer around to the Windows Service Control Manager through Windpws API functions, but I think I'm having troubles with the __stdcall convention.
I'm using MSVC 7.1.3088. For brevity I've left out information, but I think this is enough to go on:
__ExampleClass.h__ class ExampleClass { protected: void Setup( void ); void __stdcall ServiceMain( DWORD dwArgc, LPSTR *lpszArgv ); LPSERVICE_MAIN_FUNCTION m_fServiceMain; };
__ExampleClass.cpp__ void ExampleClass::Setup( void ) { boost::function<void ( DWORD, LPSTR * )> f2 = boost::bind( boost::mem_fn( &ExampleClass::ServiceMain ), this, _1, _2 ); m_fServiceMain = f2.target<void ( DWORD, LPSTR * )>( );
There seem to be two issues here. The first issue is that function::target() does something different than what you're trying to do. function::target<T>() will return a pointer to a T. If the actual object stored by the instance of boost::function has type T, you get the pointer; otherwise, you get a NULL pointer. If the code above had worked, m_fServiceMain would get a NULL pointer, because the type of the bind expression in the line before it is something big, ugly, and very hard to reproduce (but it can't be void(DWORD, LPSTR*)). The second issue is that void(DWORD, LPSTR*) is probably not the type you want, because it is not the type of a function object. To extract a function pointer, you would use, e.g., "void (*)(DWORD, LPSTR*) ". I'm sure the __stdcall needs to be in that type somewhere, but I don't know where it would go :( Doug
participants (4)
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Ben Hutchings -
Douglas Gregor -
Olenhouse, Jason