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Can anyone explain Exception Specifications as used in C++ ?
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Exception specifications are a C++ language feature that indicate the programmer's intent about the exception types that can be propagated by a function. You can specify that a function may or may not exit by an exception by using an exception specification.
If a function throws an exception not listed in its exception specification, the function unexpected(), defined in the C++ standard library, is invoked. The default behavior of unexpected() is to call terminate(). (In some situations, it may be necessary to override the actions performed by unexpected().
A function with a non-throwing dynamic exception specification does not allow any exceptions. A dynamic exception specification is not considered part of a function's type. If the function throws an exception of the type not listed in its exception specification, the function std::unexpected is called.
Dynamic exception specifications are deprecated. That's a warning from the standards committee that they might be removed in a future version of the standard. In the meantime, they are legal and their behavior is well defined.
The important thing to know is: exception specifications are deprecated in the next revision of C++, except for the no-throw specifier (throw()), which is basically officially saying "don't use them".
Putting throw() after a function means the function does not throw any exceptions. If it does anyway, the application will be terminated (probably - the unexpected handler is called), so the rest of your application can use that function knowing it will not throw an exception. This is can be handy for writing exception-safe code.
Example:
void MyFunction() throw() // does not throw any exceptions
{
/* ... */
{
They are generally regarded as a bad idea.
They say what a method will throw. The downside is that if that method throws anything else then your app terminates. So it's a guarantee but not in the same way that Java does it. And it adds the overhead of inspection.
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