Andrei Alexandrescu Wrote:
> Derek Parnell wrote:
> > On Sun, 22 Mar 2009 14:31:07 -0400, Steve Teale wrote:
> >
> >> void str()
> >> {
> >> auto s = new char[];
> >> }
> >>
> >> void main()
> >> {
> >> str();
> >> }
> >>
> >> produces:
> >>
> >> str.d(3): Error: new can only create structs, dynamic arrays or class
> >> objects, not char[]'s.
> >>
> >> What am I missing here, isn't char[] a dynamic array?
> >
> > I believe that the message is wrong, or at least misleading. The 'dynamic'
> > here does not mean variable-length arrays but not 'static' - as in ...
> > address is not known at compile time.
> >
> > The 'new' is supposed to create something on the heap and return a
> > pointer/reference to it. Thus structs, fix-length arrays, and class objects
> > are obvious candidates for that. Variable-length arrays are always created
> > on the heap anyway, so to ask for a 'new char[]' is asking for the 8-byte
> > pseudo-struct for the array to be created on the heap (which would not be
> > initialized to anything) and return a pointer to it. This would give you
> > one more level of indirection that you're probably not expecting.
> >
> > The normal way to create an empty (new, as in never been used yet) char[]
> > is simply ...
> >
> > void str()
> > {
> > char[] s;
> > }
> >
> > But you knew (no pun intended) that already.
> >
> >
> > What you were actually asking for is more like ...
> >
> > struct dynary
> > {
> > size_t len;
> > void *data;
> > }
> >
> > void str()
> > {
> > auto s = cast(char[]*)(new dynary);
> > }
> >
> > void main()
> > {
> > str();
> > }
> >
>
> I think the question is very legit. char[] is a type like any other
> type. What if I want to create a pointer to an array?
Well, thanks for that, I already got flamed for asking a beginner question! As
you say, the function of new is fuzzy, and the error message is misleading.
>
> new is a really bad construct. I'm very unhappy that D inherited it.
>
>
> Andrei
>
> P.S. The way you create a pointer to an array is:
>
> auto weird = (new char[][1]).ptr;
