I know that one can declare something extern (C) to use a function written
in C from within D source. I want to create a C function that can return
(D-type) char[].

Is this possible? I presume it'll require some C include files for the D infrastructure ...

All help gratefully received.

Matthew

"Matthew Wilson" <dmd@synesis.com.au> wrote in message news:b5e2ar$2l47$1@digitaldaemon.com...
> I know that one can declare something extern (C) to use a function written
> in C from within D source. I want to create a C function that can return
> (D-type) char[].
>
> Is this possible? I presume it'll require some C include files for the D infrastructure ...
>
> All help gratefully received.

All you need to do is return a struct that looks like this:

struct Array
{
    int length;
    void *data;
};

allocated from where?

"Walter" <walter@digitalmars.com> wrote in message news:b5eb13$2tuh$1@digitaldaemon.com...
>
> "Matthew Wilson" <dmd@synesis.com.au> wrote in message news:b5e2ar$2l47$1@digitaldaemon.com...
> > I know that one can declare something extern (C) to use a function
written
> > in C from within D source. I want to create a C function that can return
> > (D-type) char[].
> >
> > Is this possible? I presume it'll require some C include files for the D infrastructure ...
> >
> > All help gratefully received.
>
> All you need to do is return a struct that looks like this:
>
> struct Array
> {
>     int length;
>     void *data;
> };
>
>

It's returned in the register pair EDX:EAX, so it doesn't matter where it is allocated.


"Matthew Wilson" <dmd@synesis.com.au> wrote in message news:b5ehu2$3kd$1@digitaldaemon.com...
> allocated from where?
>
> "Walter" <walter@digitalmars.com> wrote in message news:b5eb13$2tuh$1@digitaldaemon.com...
> >
> > "Matthew Wilson" <dmd@synesis.com.au> wrote in message news:b5e2ar$2l47$1@digitaldaemon.com...
> > > I know that one can declare something extern (C) to use a function
> written
> > > in C from within D source. I want to create a C function that can
return
> > > (D-type) char[].
> > >
> > > Is this possible? I presume it'll require some C include files for the
D
> > > infrastructure ...
> > >
> > > All help gratefully received.
> >
> > All you need to do is return a struct that looks like this:
> >
> > struct Array
> > {
> >     int length;
> >     void *data;
> > };
> >
> >
>
>

Walter wrote:

> "Matthew Wilson" <dmd@synesis.com.au> wrote in message news:b5e2ar$2l47$1@digitaldaemon.com...
> > I know that one can declare something extern (C) to use a function written
> > in C from within D source. I want to create a C function that can return
> > (D-type) char[].
> >
> > Is this possible? I presume it'll require some C include files for the D infrastructure ...
> >
> > All help gratefully received.
>
> All you need to do is return a struct that looks like this:
>
> struct Array
> {
>     int length;
>     void *data;
> };

Walter, I know that yo ucan do this, but it is a very bad idea!  This struct is not defined in the spec, so it totally depends on the implementation of the compiler.  We need to define a standard way to do this, even if the standard is simply this.

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Russ Lewis wrote:
> Walter, I know that yo ucan do this, but it is a very bad idea!  This struct is
> not defined in the spec, so it totally depends on the implementation of the
> compiler.  We need to define a standard way to do this, even if the standard is
> simply this.

It's the same with "%.*s" printf format - it relies upon this struct
just as well. So it can be considered as a part of specification.

It is even mentioned under "memory layout" in the spec.

-i.