Exceptions: Difference between revisions

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=={{header|C++}}==

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In C++ an exception can be of any copyable type, this includes int's, other primitives, as well as objects.

C++ has no finally construct. Instead you can do this in the destructor of an object on the stack, which will be called

if an exception is thrown.

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~~The~~ exception can be of any type, this includes int's, other primitives, as well as objects.

'''Defining exceptions'''

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};</lang>

~~There's~~ ~~also~~ a ~~class~~ <tt>std::exception</tt> ~~which you can, but are not required to derive your exception class from~~. The advantage of doing so is that you can catch unknown exceptions and still get some meaningful information ~~out~~. There are also more specific classes like <tt>std::runtime_error</tt> which derive from <tt>std::exception</tt>.

However thrown exceptions should almost always derive from <tt>std::exception</tt>. The advantage of doing so is that you can catch unknown exceptions and still get some meaningful information. There are also more specific classes like <tt>std::runtime_error</tt> which also derive from <tt>std::exception</tt>.

<lang cpp>#include <exception>

struct MyException: std::exception

{

~~char~~ const* what() const ~~throw()~~ { return "description"; }

virtual const char* what() const noexcept { return "description"; }

}</lang>

Note that in principle you can throw any copyable type as exception, including built-in types.

'''Throw exceptions'''

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<lang cpp>void foo()

<lang cpp>// this function can throw any type of exception

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void foo()

{

throw MyException();

}

// this function can only throw the types of exceptions that are listed

void foo2() throw(MyException)

{

throw MyException();

}

// this function turns any exceptions other than MyException into std::bad_exception

void foo3() throw(MyException, std::bad_exception)

{

throw MyException();