Is there a way to get the string representation of HRESULT value using win API?

Question

Is there a function in win API which can be used to extract the string representation of HRESULT value?

The problem is that not all return values are documented in MSDN, for example ExecuteInDefaultAppDomain() function is not documented to return "0x80070002 - The system cannot find the file specified.", however, it does! Therefore, I was wondering whether there is a function to be used in common case.

Title is different, but essentially the answer will be the same as for [this](http://stackoverflow.com/questions/455434/how-should-i-use-formatmessage-properly-in-c) one. — Christian.K, Aug 10 '11 at 08:49

score 114 · Accepted Answer · edited Apr 17 '17 at 00:00

114

You can use _com_error:

_com_error err(hr);
LPCTSTR errMsg = err.ErrorMessage();

If you don't want to use _com_error for whatever reason, you can still take a look at its source, and see how it's done.

Don't forget to include the header comdef.h

edited Apr 17 '17 at 00:00

Shameel Mohamed

607
5
23

answered Aug 10 '11 at 08:50

Eran

21,632
6
56
89

8

A more complete sample for convenience: inline CString GetMessageForHresult(HRESULT hr) { _com_error error(hr); CString cs; cs.Format(_T("Error 0x%08x: %s"), hr, error.ErrorMessage()); return cs; } – nietras Feb 09 '12 at 15:55
5

header file required: #include – Sahil Singh Dec 22 '16 at 11:36
2

@nietras what is `CString`? – Phani Rithvij Nov 11 '19 at 15:04
@PhaniRithvij, `CString` is MFC's string type (actual C++ class, that is; not a pointer to a C string like `LPCTSTR` and such). – Eran Nov 13 '19 at 11:07
2

how we should free the errMsg? – Nusrat Nuriyev Jan 09 '21 at 03:56
@CEOatApartico the string returned by ErrorMessage will be released when the _com_error object is destructed. So you should neither free errMsg yourself nor store the returned string in some variable that outlives the _com_error object. – Eran Jan 10 '21 at 14:17
yes, I have read that in the documentation that the lifetime of the _com_error is over when it exits from a block. thank you, for your response :) – Nusrat Nuriyev Jan 12 '21 at 04:00
"To use `CString`, include the `atlstr.h` header." - Microsoft docs – Matt Kleinsmith Mar 29 '21 at 02:54

score 36 · Answer 2 · answered Jun 04 '19 at 22:57

36

Since c++11, this functionality is built into the standard library:

#include <system_error>

std::string message = std::system_category().message(hr)

answered Jun 04 '19 at 22:57

Chronial

66,706
14
93
99

3

This works for system errors, not generic `HRESULT` error codes. @che You are confusing `HRESILT` with `NT_STATUS`. Though they have similar encodings, the former is used throughout the Windows API (COM) as well as the Windows Runtime. You won't be using either one in a kernel mode module. – IInspectable Oct 07 '20 at 11:01
`_com_error` from `` nicely encapsulates all for you without using the ["dreaded" ``](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0824r1.html) ... sadly that pushes you into a windows [unresolved legacy](https://github.com/MicrosoftDocs/cpp-docs/issues/2494#issuecomment-701200395) land. We might actually reimplement that, minus the `IErrorInfo` functionality. Without using the std lib. – Chef Gladiator Oct 08 '20 at 06:28

Simon Mourier · Answer 3 · 2020-01-01T09:05:20.333

19

The Windows API for this is FormatMessage. Here is a link that explains how to do it: Retrieving Error Messages.

For Win32 messages (messages with an HRESULT that begins with 0x8007, which is FACILITY_WIN32), you need to remove the hi order word. For example in the 0x80070002, you need to call FormatMessage with 0x0002.

However, it does not always work for any type of message. And for some specific messages (specific to a technology, a vendor, etc.), you need to load the corresponding resource DLL, which is not always an easy task, because you need to find this DLL.

edited Jan 01 '20 at 09:05

answered Aug 10 '11 at 09:03

Simon Mourier

132,049
21
248
298

2

The 7 in 0x8007 is FACILITY_WIN32 and it is not FACILITY_ITF. See for example "Structure of COM Error Codes" at http://msdn.microsoft.com/en-us/library/ms690088 – Alessandro Jacopson Oct 12 '11 at 06:59
7

`HRESULT_CODE(hr)` can turn that into win32 error code – pronebird Feb 05 '18 at 14:54

score 3 · Answer 4 · answered May 26 '16 at 15:27

3

Here's a sample using FormatMessage()

LPTSTR SRUTIL_WinErrorMsg(int nErrorCode, LPTSTR pStr, WORD wLength )
{
    try
    {
        LPTSTR  szBuffer = pStr;
        int nBufferSize = wLength;

        //
        // prime buffer with error code
        //
        wsprintf( szBuffer, _T("Error code %u"), nErrorCode);

        //
        // if we have a message, replace default with msg.
        //
        FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM,
                NULL, nErrorCode,
                MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
                (LPTSTR) szBuffer,   
                nBufferSize,    
                NULL );
    }
    catch(...)
    {
    }
    return pStr;
} // End of SRUTIL_WinErrorMsg()

answered May 26 '16 at 15:27

WebDrive

1,248
12
19

3

Win32 is C. That above is a mixture of C and C++ exceptions. I am unaware that `FormatMessage` or any other Win32 function trows c++ exceptions? `FormatMessage` is returning a value and it is well documented. And. That function can not be used on raw HERROR values. HRESULT_CODE(hr) will (likely) give you the error code you need to call that function with it. – Chef Gladiator Sep 24 '20 at 06:18
1

you who have given -1 on that comment can you please explain why? I am always grateful to learn. – Chef Gladiator Sep 24 '20 at 06:26

Is there a way to get the string representation of HRESULT value using win API?

4 Answers4

Linked

Related