EXCEPINFO

EXCEPINFO is a structure defined in Windows OLE Automation used to convey detailed exception information when a COM automation call, typically IDispatch::Invoke, fails. It provides a standardized way for the callee to supply an error code, source, description, and optional help context that can be presented to scripts or applications consuming automation interfaces. The structure is declared in the OLE/Automation headers and is commonly used by language runtimes and COM components to communicate rich error information across boundaries.

Fields and meaning:

- wCode: a 16-bit error code that represents the error portion of the SCODE associated with the exception.

- wReserved: reserved and must be zero.

- bstrSource: a BSTR naming the source of the error (e.g., the component or module).

- bstrDescription: a human-readable description of the error.

- bstrHelpFile: a BSTR containing a path to a help file.

- dwHelpContext: a numeric help context identifier within the help file.

- pvReserved: reserved for future use; must be NULL.

- pfnDeferredFillIn: an optional pointer to a function for deferred filling of the structure.

Usage notes:

During an automation call, if an error occurs and DISP_E_EXCEPTION is returned, the callee fills an EXCEPINFO structure with the above fields to convey details to the caller. The BSTR members (bstrSource, bstrDescription, bstrHelpFile) are owned by the producer and must be freed by the recipient with SysFreeString after use. pvReserved should be NULL unless a deferred fill-in function is provided; in typical scenarios, pfnDeferredFillIn is not used. EXCEPINFO complements IErrorInfo on Windows by delivering structured error data suitable for automation clients and scripting languages.