From: Erik Lindblad <eriklindblad3@...>
Date: 2009-09-13T08:15:10+09:00
Subject: Re: Using Data_Make_Struct for incomplete type

On 12 Sep, 21:39, Joel VanderWerf <vj...@path.berkeley.edu> wrote:
> Erik Lindblad wrote:
> > Hi all
>
> > I am writing a Ruby wrapper for a C library. I can wrap some of the C
> > structs with Data_Make_Struct but for one of them I get "invalid
> > application of sizeof to incomplete type". I expect this has something
> > to do with that the compiler cannot find a definitive size of the
> > struct.
>
> Have you included all the relevant headers?
>
> --
>        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

Yes, I can do both Data_Wrap_Struct for other structs in the same
library, and create "instances" of the struct in question. The struct
is defined in a lib that I only have as a binary so I cannot
experiment with the source.

I have tried both with Data_Make_Struct and with a construct I found
in a blog post:

struct_name* s = (struct_name*)malloc(sizeof(struct_name));
VALUE obj;
obj = Data_Wrap_Struct(klass, 0, terminate, s);

Both result in the same compile message:

invalid application of sizeof to incomplete type s

The struct contains arrays of pointers to other structs so my guess is
that it has something to do with that the compiler cannot figure out a
definitive size to use for the struct. If that is the case I have no
idea how to work around that.

Thankful for any input.

Regards

Erik