Re: Are throwing default constructors bad style, and if so, why?
Erik Wikstr??m wrote:
On 2008-09-25 01:41, Andrei Alexandrescu wrote:
James Hopkin wrote:
On Sep 23, 1:29 am, Andrei Alexandrescu
<SeeWebsiteForEm...@erdani.org> wrote:
Mathias Gaunard wrote:
All default constructors of containers are not required to be nothrow.
Electronic Arts has asked the standard to change that, however,
showing their own EASTL as an improvement upon the STL.
I'm of the same opinion as them.
Andrei
Me too, but I don't think it implies much about whether throwing
default constructors *in general* are problematic.
I agree. So let me restart. Do you agree that in a GC system, there
should be _some_ constructor that doesn't throw (that being the
constructor called when the object enters the destroyed state)? If we do
agree on that, what remains is to define that constructor.
Perhaps it is the destructor that should be used to enter the destroyed
state. This might just be a question of terminology but I find it hard
to accept that a constructor is used to enter a destroyed state. I think
that one needs to keep the build-up and tear-down as two separate
activities, even though they might result in the same state for the
object. Of course, if the destructor is used to enter the destroyed
state I see no need to place any restrictions on the constructors.
Yah, so it looks. So tear-down should bring the object to a state that:
(a) is detectable;
(b) can be entered via a nothrow operation (is this really necessary?);
(c) is actively checked by all functions in the interface of the object;
(d) actively prevents reallocation.
It is up to the type to decide what to do about (c). For example, should
vector::empty throw, or just advertise an empty object? How about a
is_open called on a zombie File, should it throw or return false? For
the sake of bug detection and prevention, I'd say throw first and ask
second :o).
Andrei
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