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Re: ctor unnecessarily wiping of PODs
On 19 March 2012 18:27, Hite, Christopher wrote:
> Thanks for the quick response.
>> The C++ standard says that for a POD type the initializer () will cause it to be zero-initialized.
> No the standard says: If I don't init the POD with an initializer or otherwise, I have to expect dirty memory there.
Where does it say that?
[dcl.init] paragraph 10 says "An object whose initializer is an empty
set of parentheses, i.e., (), shall be value-initialized."
[dcl.init] paragraph 11 says "If no initializer is specified for an
object, the object is default-initialized; if no initialization is
performed, an object with automatic or dynamic storage duration has
indeterminate value."
Your example has an initializer which is an empty set of parentheses.
> n and u are being inited even with the default constructor. ?With ctor uncommented I would expect n() to init just n and the array to be uninitialized.
Correct. Which is what I see with GCC 4.6.1 or later (I don't have
4.6.0 available)
>> If that's not what you want, use:
>> ? ? ?new (v) Ray2;
>> void makeRay(void*v){
>> ? ? ? new(v)Ray2;
>> }
> Does the same thing. ?Semantics are identical.
Not for me.
It's possible this was a bug in 4.6.0 that is fixed in the current release.