COM component Design and application (12)--Error and exception handling

This article supporting source code

First, the preface

In programming, error handling is essential and usually takes up a lot of space. This read the method of handling errors (exceptions) that are landed in COM.

In a component program, if you encounter an error, there are generally two ways to handle it.

Second, simple return

For simpler errors, return directly to the HRESULT that represents the cause of the error. For example, here are some common error values:

E_invalidarg	0x80070057	Parameter error
E_outofmemory	0x8007000e	Memory error
E_NotImpl	0x80004001	Not implemented
E_pointer	0x80004003	Invalid pointer
E_handle	0x80070006	Invalid handle
E_abort	0x80004004	Terminate operation
E_accessdenied	0x80070005	Access Denied
E_nointerface	0x80004002	Interface not supported

Alternatively, you can return to construct an HRESULT error value yourself. method is to use the macro Make_hresult (Sev,fac,code)

Parameters	Meaning	Value (binary)
SEv Severity	Success	00
Successful but there are some report information	01
Warning	10
Error	11
FAC Device Information	Facility_aaf	00000010010
Facility_acs	00000010100
Facility_backgroundcopy	00000100000
Facility_cert	00000001011
Facility_complus	00000010001
Facility_configuration	00000100001
Facility_control	00000001010
Facility_dispatch	00000000010
Facility_dplay	00000010101
Facility_http	00000011001
Facility_internet	00000001100
Facility_itf	00000000100
Facility_mediaserver	00000001101
Facility_msmq	00000001110
Facility_null	00000000000
Facility_rpc	00000000001
Facility_scard	00000010000
Facility_security	00000001001
Facility_setupapi	00000001111
Facility_sspi	00000001001
Facility_storage	00000000011
Facility_sxs	00000010111
Facility_umi	00000010110
Facility_urt	00000010011
Facility_win32	00000000111
Facility_windows	00000001000
Facility_windows_ce	00000011000
Code unique error code	16 bits (bit) you define yourself.

Once the caller gets the HRESULT value returned, you can also use the macro hresult_severity (), hresult_facility (), Hresult_code () to obtain SEV error levels, FAC device information, and code error codes.