C++ exception specification - handling not valid exceptions

Question

What is the standard behavior in cases when function throws exception not in valid exception list ? For example when I run this code:

#include <iostream>
#include <cstdlib>

using namespace std;

void NotLegal() throw(char) {
    throw 42;
}

void myunexpected () {
  cout << "exception not in list\n";
  cin.get();
  exit(0);
}

int main()
{
    set_unexpected(myunexpected);

    try {
       NotLegal();
   }
   catch(...) {
       cout << "exception catched";
       cin.get();
   }

   return 0;
}

It behaves differently on GCC and Visual Studio C++ compilers:

• On VS 2010 not expected exception is catched in general exception handler.
• On GCC unexpected() handler function is called instead of catching exception.

Why is this difference ? Why MS C++ compiler doesn't calls unexpected() callback ?

Answer 1

The documentation for set_unexpected calls out this behaviour:

Remarks

...

The C++ Standard requires that unexpected is called when a function throws an exception that is not on its throw list. The current implementation does not support this.