Re: C++0x/1x exception specifications proposal: Compile-time checked
maihem@gmail.com wrote:
On Feb 18, 1:49 pm, Pavel Minaev <int...@gmail.com> wrote:
On Feb 17, 5:12 pm, mai...@gmail.com wrote:
It's quite the opposite. Restriction on exception specs on
inheritance follow directly from Liskov substitution principle,
which as about as OOP as it can be. If a override implementation
of a function throws some exception that the original function did
not specify as throwing, then how can one safely do polymorphic
calls to such a function at all?
With all the post-Java OOP languages - you have to assume that
anything may be thrown. The problem is that extending functionality
by deriving naturally leads to more branches and thus more things
to go wrong. The creator of an interface can't know what things
derived types would want to throw because they can't know what the
derived classes might do.
What do you mean?!
The creator of the derived classes pretty damn well has to follow the
requirements of the interface. How am I to call a virtual function, if
I don't know what it does?
I wouldn't say people don't use specs for that reason by everyone.
Personally, I don't use them because they don't enforce throw spec
compliance at compile-time, and doing it at runtime serves little
point - as far as I'm concerned, there's little difference between
not catching an unexpected exception, and having it caught for you
and unexpected() called. I want to know if my code is safe before
it runs.
Calling std::unexpected is actually worse, throwing a disallowed
exception acts like it first removes all destructors from the
cleanup schedule and /then/ throws.
If a function has proven a breach of contract, by throwing an
exception the throw spec says is never should, this function cannot be
trusted in any other way either. How do we know that any values
touched by it is correct?
Better pull the emergency break, as fast as possible!
Bo Persson
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