Re: An exception that throws while it is being thrown, no terminate?

From:
"Niels Dekker - no reply address" <invalid@this.is.invalid>
Newsgroups:
microsoft.public.vc.language
Date:
Thu, 3 Dec 2009 18:32:29 +0100
Message-ID:
<#ljSz4DdKHA.2184@TK2MSFTNGP04.phx.gbl>
Martin B. wrote:

How do you verify that the copy-ctor is called?
Have you added some tracing, do you set a breakpoint?


Yes, when I run within Visual Studio 2008, having a breakpoint in the
copy-constructor, it gets there.

Are you running the process under the debugger?
release/debug compilation?


I tried both debug and compilation. Neither of them appear to do an
std::terminate. Both compilations produce a similar output:

  First-chance exception at 0x... in MyTest.exe: Microsoft C++ exception:
std::bad_alloc at memory location 0x...
  The program '[...] MyTest.exe: Native' has exited with code 1 (0x1).

What operating system are you using exactly?


Windows XP Professional.

Are you able to reproduce it? Maybe a slightly extended main() function
could be helpful, as follows:

  //////////////////////////////////////////////////
  int main()
  {
    const MyException constException("what");
    try
    {
      // Here the copy-constructor is called:
      throw constException;
    }
    catch( MyException & referenceToMyException )
    {
      // Modify the exception. So this must be a copy!
      // Note that we don't actually get here.
      referenceToMyException = MyException("");
    }
    catch( std::bad_alloc & )
    {
      // Here is where we get!
      return EXIT_FAILURE;
    }
    // This line is never reached.
    return 0;
  }

  //////////////////////////////////////////////////

Here I hope you see more clearly that constException *must* be copied, in
order to support the /potential/ assignment to referenceToMyException. (Note
that the original exception object is "const".) Also I added "return 0" at
the end, for clarity. Although it is never reached, because the program
always returns EXIT_FAILURE, when compiled on VC. Please let me know if you
agree that std::terminate should be called instead!

Kind regards,

  Niels
--
Niels Dekker
http://www.xs4all.nl/~nd/dekkerware
Scientific programmer at LKEB, Leiden University Medical Center

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