Re: Exception Handling in Release Mode

From:

"Michael Kilburn" <crusader.mike@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Fri, 16 Feb 2007 19:12:35 CST

Message-ID:

<1171661222.508762.283920@v33g2000cwv.googlegroups.com>

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On Feb 15, 10:49 pm, "Moahn" <ramamo...@rediffmail.com> wrote:

  It is working fine in Win32 Debug build, but it is not catching the
exception in Win32Release mode.

int main(int argc, char* argv[])
{
  int i = 0;

  try
  {
       int m = 17/i;
  }
  catch(...)
  {
       cout<<"Main - Catch"<<endl;
  }
  cout <<"End of Main" <<endl;

  return 0;

}

Could you please explain, why the Exception is not caught in the
Win32Release mode.??

Well, it looks like nobody gave you full explanation of what's going
on here. Basically, in C++ Win32 world on x86 platform there are:
- Structured exceptions -- "hard" errors, usually 'divide by zero' or
'access violation'; they are usually generated by processor when it
stumbles upon related condition (read MSDN about __try/__except)
- C++ exceptions -- these basically are glorified function calls (you
could think of 'throw' as a 'call special function')

Your program generates SE. Ability to catch SE with 'catch(...)' -- is
the very bad idea implemented long ago, MS struggled to drop this
"feature" for quite a while since then. And your example is just one
of many that show why it should not be like this. Another, more
illustrating, is:

int i = 0;
try
{
     MyClass mc;
     int m = 17/i;
}
catch(...)
{
}

Outcome: mc's destructor won't ever be called.

Now, why it does not get caught in Release mode: because optimizer
kicks in. From his point of view try/catch clause is unnecessary (no
function calls, no 'throw' statements) -- it simply optimizes it away.
But if you really want compiler to treat every operation as one that
could throw -- use asynchronous exception model (see MSDN). It could
slow your code performance considerably though... According to rumors
SQL2k's engine is compiled with this option. ;-)

Oh, and yes -- get yourself better compiler (gcc or latest MS VC), it
is bad to learn C++ using seriously flawed C++ compiler -- it is like
studying microbiology using broken microscope

Bye.
Sincerely yours, Michael.

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