What is the case against a struct post-blit default constructor?

[Andrei Alexandrescu]

On 10/11/12 9:56 AM, deadalnix wrote:
> Le 11/10/2012 14:19, Andrei Alexandrescu a écrit :
>> Could you please give a few examples? (Honest question.) Most structures
>> I define have an obvious quiescent state that vacuously satisfies the
>> invariant. Exceptions that come to mind are: (a) value types that must
>> always allocate something on the heap, see e.g. the contortions in
>> std.container; (b) values as permits (the existence of the value
>> guarantees a resource has been secured, as in scoped locks on mutexes).
>>
>
> invariant will explode at you face at runtime any time you use the
> struct wrong where a default constructor would have prevented such use
> in the first place.

I just mentioned that most of my structs have a natural 
invariant-abiding state.

> Worse, the faulty case can be created at any place where the struct is
> used and is likely to create a problem.
>
> In fact, such design rely on the well known « a good programmer don't do
> .... » which is known to be a very good way to design hard to use and
> error prone constructs.

There's a misunderstanding here.


Andrei