Windows Mobile Developer Network

Question

When I use #import directive I get the following compile error: error C2065: ‘_com_issue_errorex’ : undeclared identifier. The same code works OK on PC. Can I use smart pointers and #import directive on Pocket PC? How can I use them?

Answer

_com_issue_error and _com_issue_errorex functions that are used in smart pointers are not defined in eVC++. You should define them yourself or use STUtil library that defines them. These functions are not defined because they use C++ exceptions that are not supported in eVC++.
Smart pointers uses exceptions to inform about error HRESULT return code. Method of smart pointer are wrappers to corresponding methods of wrapped COM interface like:

inline _bstr_t IConverter::IntToString ( int nValue ) {
BSTR _result;
HRESULT _hr = raw_IntToString(nValue, &_result);
if (FAILED(_hr)) _com_issue_errorex(_hr, this, __uuidof(this));
return _bstr_t(_result, false);
}


This method was defined in IDL as

HRESULT IntToString([in] INT nValue, [out, retval] BSTR *pResult);


As we see the method of the smart pointer return value of the [retval] parameter. But return value was used for error information. Smart pointers uses _com_issue_errorex function that throws C++ exceptions.

Using STUtil library

1. Download STUtil library and add STUtil.h and STUtil.cpp files into your project.
2. Add include of STUtil.h file into Stdafx.h file.
3. Use smart pointers. Smart pointers will throw exceptions that could be caught by __except (CATCH_COM_ERROR) code.
4. Check COM error code by using GetComError() function that returns CSTComError object.
5. If you want ignore COM error define ST_IGNORE_COM_EXCEPTIONS macro (using #define ST_IGNORE_COM_EXCEPTIONS) in your Stdafx.h file. In that case no exception will be thrown, all COM error codes will be ignored.

Source code

Here is a sample code that uses exceptions.

In StdAfx.h file:

#include "STUtil.h"

In custom .cpp code:

IConverterPtr cnv;
_bstr_t str;
__try {
cnv.CreateInstance(_T("Test.Converter"));
str = cnv->IntToString(46);
}
__except (CATCH_COM_ERROR) {
switch (GetComError().Error()) {
case E_FAIL:
::AfxMessageBox(_T("E_FAIL"));
break;
case E_INVALIDARG:
::AfxMessageBox(_T("E_InvalidArg"));
break;
}
}


Here is a sample code that doesn’t use exceptions (ignores COM errors).

In StdAfx.h file:

#define ST_IGNORE_COM_EXCEPTIONS
#include "STUtil.h"

In custom .cpp code:

IConverterPtr cnv(_T("Test.Converter"));
_bstr_t str = cnv->IntToString(46);


Related resources:

Section: COM/ActiveX
Library: STUtil

(Discuss in forum)