<h2>Question</h2> When I use #import directive I get the following compile error: <i>error C2065: '_com_issue_errorex' : undeclared identifier.</i> The same code works OK on PC. Can I use smart pointers and #import directive on Pocket PC? How can I use them?
<h2>Answer</h2> <i>_com_issue_error</i> and <i>_com_issue_errorex</i> functions that are used in smart pointers are not defined in eVC++. You should define them yourself or use <a href="/libraries/stutil.html">STUtil</a> 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:
Code:
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
Code:
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.
<h3>Using STUtil library</h3> <ol> <li>Download <a href="/libraries/stutil.html">STUtil</a> library and add <i>STUtil.h</i> and <i>STUtil.cpp</i> files into your project.</li> <li>Add include of <i>STUtil.h</i> file into <i>Stdafx.h</i> file.</li> <li>Use smart pointers. Smart pointers will throw exceptions that could be caught by <i>__except (CATCH_COM_ERROR)</i> code.</li> <li>Check COM error code by using GetComError() function that returns CSTComError object.</li> <li>If you want ignore COM error define ST_IGNORE_COM_EXCEPTIONS macro (using <i>#define ST_IGNORE_COM_EXCEPTIONS</i>) in your <i>Stdafx.h</i> file. In that case no exception will be thrown, all COM error codes will be ignored.</li> </ol>
<h2>Source code</h2> Here is a sample code that uses exceptions.
Code:
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).
Code:
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);
<h2>Related resources:</h2>
<img src="http://www.pocketpcdn.com/images/bullet.gif" width="22" height="15"><a href="/sections/com.html">Section: COM/ActiveX</a>
<img src="http://www.pocketpcdn.com/images/bullet.gif" width="22" height="15"><a href="/libraries/stutil.html">Library: STUtil</a>
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