Re: Exception Handling in Release Mode

From:
"PeteK" <pete_k_1955@yahoo.co.uk>
Newsgroups:
comp.lang.c++.moderated
Date:
Fri, 16 Feb 2007 07:58:47 CST
Message-ID:
<1171621032.222115.158370@p10g2000cwp.googlegroups.com>

There is no exception being thrown in this code. What you are seeing in
debug mode seems to be a platform (i.e. Windows) specific extension that
converts certain runtime errors, such as an integer division by zero,
into C++ exceptions. That is, your code is turned into something to the
effect of:

    try
    {
    #ifndef _NDEBUG
       if (i == 0)
          throw DivisionByZeroException();
    #endif

       int m = 17/i;
    }


Before we get to the platform-specific stuff let's answer the original
question - "Why don't I catch an exception is release mode"

The answer is simple. In release mode the compiler has optimised away
the division. The code basically becomes:

int main(int argc, char* argv[])
{
  cout <<"End of Main" <<endl;
  return 0;
}

It is allowed to do this because, from a C++ point of view, the other
code has no observable effect.

Next the platform specific stuff. Microsoft use exactly the same
exception handling mechanism to handle C++ exceptions and OS/HW
exceptions, so catch(...) will catch exceptions of all types
(including a HW generated zero divide). This can happen in both debug
and release modes (depending on the compiler settings - see Daniel
Krugler's post).

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