Re: Try and catch use

From:
Ulrich Eckhardt <eckhardt@satorlaser.com>
Newsgroups:
microsoft.public.vc.language
Date:
Mon, 11 Dec 2006 12:29:22 +0100
Message-ID:
<k1sv44-3is.ln1@satorlaser.homedns.org>
Eitan M wrote:

_ConnectionPtr m_pConn;
...
  HRESULT hr;
  char errStr[1024];

  try
  {
    ::CoInitialize(NULL);
    hr = m_pConn.CreateInstance (__uuidof(Connection));
    m_pConn->ConnectionString = TEXT("....");
    m_pConn->Open(m_pConn->ConnectionString, "", "", adModeUnknown);
...
  } // try
  catch (exception& e)
  {
...
  }

,but still I have a problem :
If DB cannot be openned, the exceptions are not catched !


FYI, the past tense of 'catch' is 'caught', not 'catched' and not 'cought'.

Anyhow, back to C++: if m_pConn->Open() throws an 'exception', the above
code should catch it. However, I guess this is COM code, and COM doesn't
(AFAIK) use C++ exceptions but some other means to signal errors. IOW, I
guess that you are handling the wrong type of errors for the code. Look up
the documentation what it says about error handling.

Further, I see two things in above code:
1. 'hr' is never checked
Maybe you just didn't show that code, but if CreateInstance() fails you
can't just continue like that.
2. 'exception& e'
You can catch all exceptions thrown by the C++ standard library
with 'std::exception const& e'. Note both the 'std::' qualifier and
the 'const'. The former is necessary because the whole C++ stdlib in that
namespace while the latter is just to document that you don't intend to
modify the exception object.

If you want further assistance, it would be helpful if you provided some
more information about where exactly an exception is thrown and what type.
Quote debug messages if you see any relevant ones and also provide a URL to
the docs of whatever COM code you use (if possible). Otherwise this is too
much guessing.

Uli

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