COM System Functions

So COM is complex and unfortantely there are many toolkits and layers that are designed to help but actually can obscure understanding.  Sometimes, it is better to know the underlying mechanism and in COM so very often this means calling a System function.  These system functions are exported by well know COM dlls like OLE32.DLL and OLEAUT32.DLL.

On this page we show all the functions that these DLLs export so they can be browsed.

Array Manipulation Functions	Decimal Arithmetic Functions	String Manipulation Functions
SafeArrayAccessData	VarDecAbs	SysAddRefString
SafeArrayAddRef	VarDecAdd	SysAllocString
SafeArrayAllocData	VarDecCmp	SysAllocStringByteLen
SafeArrayAllocDescriptor	VarDecCmpR8	SysAllocStringLen
SafeArrayAllocDescriptorEx	VarDecDiv	SysFreeString
SafeArrayCopy	VarDecFix	SysReAllocString
SafeArrayCopyData	VarDecInt	SysReAllocStringLen
SafeArrayCreate	VarDecMul	SysReleaseString
SafeArrayCreateEx	VarDecNeg	SysStringByteLen
SafeArrayCreateVector	VarDecRound	SysStringLen
SafeArrayCreateVectorEx	VarDecSub	Type Building Functions
SafeArrayDestroy	Dispatch functions	CreateTypeLib
SafeArrayDestroyData	CreateDispTypeInfo	CreateTypeLib2
SafeArrayDestroyDescriptor	CreateStdDispatch	OaBuildVersion
SafeArrayGetDim	DispCallFunc	Type Description Functions
SafeArrayGetElement	DispGetIDsOfNames	LHashValOfNameSys
SafeArrayGetElemsize	DispGetParam	LHashValOfNameSysA
SafeArrayGetIID	DispInvoke	LoadRegTypeLib
SafeArrayGetLBound	Error-Handling Functions	LoadTypeLib
SafeArrayGetRecordInfo	CreateErrorInfo	LoadTypeLibEx
SafeArrayGetUBound	GetErrorInfo	OaEnablePerUserTLibRegistration
SafeArrayGetVartype	SetErrorInfo	QueryPathOfRegTypeLib
SafeArrayLock	Formatting Functions	RegisterTypeLib
SafeArrayPtrOfIndex	VarFormat	RegisterTypeLibForUser
SafeArrayPutElement	VarFormatCurrency	UnRegisterTypeLib
SafeArrayRedim	VarFormatDateTime	UnRegisterTypeLibForUser
SafeArrayReleaseData	VarFormatFromTokens	UDT Functions and Interfaces
SafeArrayReleaseDescriptor	VarFormatNumber	ClearCustData
SafeArraySetIID	VarFormatPercent	GetRecordInfoFromGuids
SafeArraySetRecordInfo	VarMonthName	GetRecordInfoFromTypeInfo
SafeArrayUnaccessData	VarTokenizeFormatString	Variant Arithmetic Functions
SafeArrayUnlock	VarWeekdayName	VarAbs
BSTR and Vector Conversion Functions	Numeric Parsing Functions	VarAdd
BstrFromVector	VarNumFromParseNum	VarAnd
SetOaNoCache	VarParseNumFromStr	VarCat
VarBstrCat	OLE and Data Transfer	VarCmp
VarBstrCmp	OleCreateFontIndirect	VarDiv
VectorFromBstr	OleCreatePictureIndirect	VarEqv
COM Fundamentals	OleLoadPicture	VarFix
DllCanUnloadNow	OleLoadPictureEx	VarIdiv
DllGetClassObject	Picture Functions	VarImp
DllRegisterServer	OleLoadPictureFile	VarInt
DllUnregisterServer	OleLoadPictureFileEx	VarMod
OleIconToCursor	OleSavePictureFile	VarMul
Controls and Property Pages	Registration Functions	VarNeg
OleCreatePropertyFrame	GetActiveObject	VarNot
OleCreatePropertyFrameIndirect	RegisterActiveObject	VarOr
OleLoadPicturePath	RevokeActiveObject	VarPow
OleTranslateColor	RPC Data Marshaling Functions	VarR4CmpR8
Currency Arithmetic Functions	BSTR_UserFree	VarR8Pow
VarCyAbs	BSTR_UserFree64	VarR8Round
VarCyAdd	BSTR_UserMarshal	VarRound
VarCyCmp	BSTR_UserMarshal64	VarSub
VarCyCmpR8	BSTR_UserSize	VarXor
VarCyFix	BSTR_UserSize64	Variant Manipulation Functions
VarCyInt	BSTR_UserUnmarshal	VariantChangeType
VarCyMul	BSTR_UserUnmarshal64	VariantChangeTypeEx
VarCyMulI4	VARIANT_UserUnmarshal64	VariantClear
VarCyMulI8	VARIANT_UserUnmarshal	VariantCopy
VarCyNeg	VARIANT_UserSize64	VariantCopyInd
VarCyRound	VARIANT_UserSize	VariantInit
VarCySub	VARIANT_UserMarshal64	(not documented)
Date and Time Conversion Functions	VARIANT_UserMarshal	OACreateTypeLib2
DosDateTimeToVariantTime	VARIANT_UserFree64	OACleanup
GetAltMonthNames	VARIANT_UserFree	HWND_UserUnmarshal64
SystemTimeToVariantTime	LPSAFEARRAY_UserUnmarshal64	HWND_UserUnmarshal
VarDateFromUdate	LPSAFEARRAY_UserUnmarshal	HWND_UserSize64
VarDateFromUdateEx	LPSAFEARRAY_UserSize64	HWND_UserSize
VariantTimeToDosDateTime	LPSAFEARRAY_UserSize	HWND_UserMarshal64
VariantTimeToSystemTime	LPSAFEARRAY_UserMarshal64	HWND_UserMarshal
VarUdateFromDate	LPSAFEARRAY_UserMarshal	HWND_UserFree64
	LPSAFEARRAY_UserFree64	HWND_UserFree
	LPSAFEARRAY_UserFree
	LPSAFEARRAY_Unmarshal
	LPSAFEARRAY_Size
	LPSAFEARRAY_Marshal

What is also exported from OleAut32.dll is a whole number of Variant conversion functions which are best presented cross-tabulated.

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So another nice dll is OleDlg.dll which seems to be a repository of OLE and Data Transfer dialogs. Most of the entry points are duplicated with A meaning Windows 98 and W meaning Windows 2000 onwards.

oleDlg.dll
OleUIAddVerbMenuA	OleUIAddVerbMenuW
OleUIBusyA	OleUIBusyW
OleUICanConvertOrActivateAs
OleUIChangeIconA	OleUIChangeIconW
OleUIChangeSourceA	OleUIChangeSourceW
OleUIConvertA	OleUIConvertW
OleUIEditLinksA	OleUIEditLinksW
OleUIInsertObjectA	OleUIInsertObjectW
OleUIObjectPropertiesA	OleUIObjectPropertiesW
OleUIPasteSpecialA	OleUIPasteSpecialW
OleUIPromptUserA	OleUIPromptUserW
OleUIUpdateLinksA	OleUIUpdateLinksW

And now from OLE32.DLL which is the daddy of all COM System DLLs. Breaking it down first we have the error info functions

Automation - Error Info
CreateErrorInfo	GetErrorInfo	SetErrorInfo

Also from OLE32.DLL a chunk of funcitons that handle OLE and Data Transfer such as clipboards, links, drag and drop.

OLE and Data Transfer
CreateDataAdviseHolder	CreateDataCache	CreateOleAdviseHolder
DoDragDrop	OleCreate	OleCreateDefaultHandler
OleCreateEmbeddingHelper	OleCreateEx	OleCreateFromData
OleCreateFromDataEx	OleCreateFromFile	OleCreateFromFileEx
OleCreateLink	OleCreateLinkEx	OleCreateLinkFromData
OleCreateLinkFromDataEx	OleCreateLinkToFile	OleCreateLinkToFileEx
OleCreateMenuDescriptor	OleCreateStaticFromData	OleDestroyMenuDescriptor
OleDraw	OleDuplicateData	OleFlushClipboard
OleGetClipboard	OleInitialize	OleIsCurrentClipboard
OleIsRunning	OleLoad	OleLoadFromStream
OleLockRunning	OleMetafilePictFromIconAndLabel	OleNoteObjectVisible
OleQueryCreateFromData	OleQueryLinkFromData	OleRegEnumFormatEtc
OleRegEnumVerbs	OleRun	OleSave
OleSaveToStream	OleSetClipboard	OleSetContainedObject
OleSetMenuDescriptor	OleTranslateAccelerator	OleUIAddVerbMenu
OleUninitialize	RegisterDragDrop	ReleaseStgMedium
RevokeDragDrop

Also in OLE32.Dll function concerning Structured Storage

Structured Storage
CreateILockBytesOnHGlobal	CreateStreamOnHGlobal
FmtIdToPropStgName	FreePropVariantArray
GetConvertStg	GetHGlobalFromILockBytes
GetHGlobalFromStream	OleConvertIStorageToOLESTREAM
OleConvertIStorageToOLESTREAMEx	OleConvertOLESTREAMToIStorage
OleConvertOLESTREAMToIStorageEx	PropStgNameToFmtId
PropVariantClear	PropVariantCopy
ReadClassStg	ReadClassStm
ReadFmtUserTypeStg	StgConvertPropertyToVariant
SetConvertStg	StgConvertVariantToProperty
StgCreateDocfile	StgCreateDocfileOnILockBytes
StgCreatePropSetStg	StgCreatePropStg
StgCreateStorageEx	StgGetIFillLockBytesOnFile
StgGetIFillLockBytesOnILockBytes	StgIsStorageFile
StgIsStorageILockBytes	StgOpenAsyncDocfileOnIFillLockBytes
StgOpenPropStg	StgOpenStorage
StgOpenStorageEx	StgOpenStorageOnILockBytes
StgPropertyLengthAsVariant	StgSetTimes
WriteClassStg	WriteClassStm
WriteFmtUserTypeStg

Finally, the canonical functions described as COM Fundamentals.

COM Fundamentals
BindMoniker	CLSIDFromProgID
CLSIDFromProgIDEx	CLSIDFromString
CoAddRefServerProcess	CoAllowSetForegroundWindow
CoAllowUnmarshalerCLSID	CoCancelCall
CoCopyProxy	CoCreateFreeThreadedMarshaler
CoCreateGuid	CoCreateInstance
CoCreateInstanceEx	CoCreateInstanceFromApp
CoDisableCallCancellation	CoDisconnectContext
CoDisconnectObject	CoDosDateTimeToFileTime
CoEnableCallCancellation	CoEnterApplicationThreadLifetimeLoop
CoFileTimeNow	CoFileTimeToDosDateTime
CoFreeAllLibraries	CoFreeLibrary
CoFreeUnusedLibraries	CoFreeUnusedLibrariesEx
CoGetApartmentType	CoGetCallContext
CoGetCallerTID	CoGetCancelObject
CoGetClassObject	CoGetContextToken
CoGetCurrentLogicalThreadId	CoGetCurrentProcess
CoGetInstanceFromFile	CoGetInstanceFromIStorage
CoGetInterceptor	CoGetInterfaceAndReleaseStream
CoGetMalloc	CoGetMarshalSizeMax
CoGetObject	CoGetObjectContext
CoGetPSClsid	CoGetStandardMarshal
CoGetStdMarshalEx	CoGetSystemSecurityPermissions
CoGetTreatAsClass	CoHandlePriorityEventsFromMessagePump
CoImpersonateClient	CoIncrementMTAUsage
CoInitialize	CoInitializeEx
CoInitializeSecurity	CoInstall
CoInvalidateRemoteMachineBindings	CoIsHandlerConnected
CoIsOle1Class	CoLoadLibrary
CoLockObjectExternal	CoMarshalHresult
CoMarshalInterface	CoMarshalInterThreadInterfaceInStream
CoQueryAuthenticationServices	CoQueryClientBlanket
CoQueryProxyBlanket	CoRegisterActivationFilter
CoRegisterChannelHook	CoRegisterClassObject
CoRegisterInitializeSpy	CoRegisterMallocSpy
CoRegisterMessageFilter	CoRegisterPSClsid
CoRegisterSurrogate	CoRegisterSurrogateEx
CoReleaseMarshalData	CoReleaseServerProcess
CoResumeClassObjects	CoRevertToSelf
CoRevokeClassObject	CoRevokeInitializeSpy
CoRevokeMallocSpy	CoSetCancelObject
CoSetMessageDispatcher	CoSetProxyBlanket
CoSuspendClassObjects	CoSwitchCallContext
CoTaskMemAlloc	CoTaskMemFree
CoTaskMemRealloc	CoTestCancel
CoTreatAsClass	CoUninitialize
CoUnmarshalHresult	CoUnmarshalInterface
CoWaitForMultipleHandles	CoWaitForMultipleObjects
CreateAntiMoniker	CreateBindCtx
CreateClassMoniker	CreateFileMoniker
CreateGenericComposite	CreateItemMoniker
CreateObjrefMoniker	CreatePointerMoniker
DllDebugObjectRPCHook	DllGetClassObject
DllRegisterServer	GetClassFile
GetRunningObjectTable	IIDFromString
IsAccelerator	IsEqualGUID
MkParseDisplayName	MonikerCommonPrefixWith
MonikerRelativePathTo	OleDoAutoConvert
OleGetAutoConvert	OleGetIconOfClass
OleGetIconOfFile	OleRegGetMiscStatus
OleRegGetUserType	OleSetAutoConvert
ProgIDFromCLSID	StringFromCLSID
StringFromGUID2	StringFromIID