A throw-expression with no operand in C++

A throw-expression with no operand re-throws the exception currently being handled. Such an expression should appear only in a catch handler or in a function called from within a catch handler. The re-thrown exception object is the original exception object (not a copy). For example:

try {
    throw CSomeOtherException();
}
catch(...) {  // Handle all exceptions
    // Respond (perhaps only partially) to exception
    // ...
    throw;       // Pass exception to some other handler
}

An empty throw statement tells the compiler that the function does not throw any exceptions. It is the equivalent to using__declspec(nothrow). For example:

// exceptions_trycatchandthrowstatements3.cpp 
void empty() throw()
{
   puts("In empty()");
}

void with_type() throw(int)
{
   puts("Will throw an int");
   throw(1);
}

int main()
{
   try {
       empty();
       with_type();
   }catch (int){
       puts("Caught an int");
   }
}