_set_com_error_handler

Article
08/03/2021

Replaces the default function that is used for COM error-handling. _set_com_error_handler is Microsoft-specific.

Syntax

void __stdcall _set_com_error_handler(
   void (__stdcall *pHandler)(
      HRESULT hr,
      IErrorInfo* perrinfo
   )
);

Parameters

pHandler
Pointer to the replacement function.

hr
HRESULT information.

perrinfo
IErrorInfo object.

Remarks

By default, _com_raise_error handles all COM errors. You can change this behavior by using _set_com_error_handler to call your own error-handling function.

The replacement function must have a signature that is equivalent to that of _com_raise_error.

Example

// _set_com_error_handler.cpp
// compile with /EHsc
#include <stdio.h>
#include <comdef.h>
#include <comutil.h>

// Importing ado dll to attempt to establish an ado connection.
// Not related to _set_com_error_handler
#import "C:\Program Files\Common Files\System\ado\msado15.dll" no_namespace rename("EOF", "adoEOF")

void __stdcall _My_com_raise_error(HRESULT hr, IErrorInfo* perrinfo)
{
   throw "Unable to establish the connection!";
}

int main()
{
   _set_com_error_handler(_My_com_raise_error);
   _bstr_t bstrEmpty(L"");
   _ConnectionPtr Connection = NULL;
   try
   {
      Connection.CreateInstance(__uuidof(Connection));
      Connection->Open(bstrEmpty, bstrEmpty, bstrEmpty, 0);
   }
   catch(char* errorMessage)
   {
      printf("Exception raised: %s\n", errorMessage);
   }

   return 0;
}

Exception raised: Unable to establish the connection!

Requirements

Header: <comdef.h>

Lib: If the /Zc:wchar_t compiler option is specified (the default), use comsuppw.lib or comsuppwd.lib. If the /Zc:wchar_t- compiler option is specified, use comsupp.lib. For more information, including how to set this option in the IDE, see /Zc:wchar_t (wchar_t Is Native Type).