From: matz@... (Yukihiro Matsumoto)
Date: 2001-02-04T03:30:40+09:00
Subject: [ruby-talk:10314] Re: More C API examples?

Hi,

In message "[ruby-talk:10311] More C API examples?"
    on 01/02/04, Amos <amos+lists.ruby-talk@utdallas.edu> writes:

|I was wondering if someone has examples of defining and then
|instantiating class objects in the C API.  While I see stuff like
|NEWOBJ and rb_class_new in the Ruby source code, it's not mentioned
|specifically in the README.EXT nor in the "pickaxe" book, so I was
|hoping to find more examples of how this should be done.

Don't use NEWOBJ() in your extension, since it requires own unique
T_XXXX identity number for each object type, which, I think, is
special privilege of the interpreter itself.  That is the reason why
it is not explained in README.EXT nor "pickaxe" book.

I recommend you to use Wrap_Data_Struct() and the like.

|Don't know, so thought I'd give it a try.  At least it would be a
|learning experience. 

To satisfy your curiosity, obey following steps to add new type into
the interpreter:

 (1) define new and unique T_XXX value in ruby.h. it must be less than
     0x40 and strictly UNIQUE from other type (T_XXX) values.

 (2) create object using NEWOBJ(varname, struct), a created object
     will be assigned to varname, whose type is a pointer to struct.
     varname is declared internally in the macro, so that it must be
     a first statement (after declarations) in the function/block.

 (3) set up type information of a new object using OBJSETUP().  DO NOT
     FORGET THIS.  if you forget, the program might be crash.

 (4) modify gc.c.  add T_XXX entry to rb_gc_mark() and obj_free().  DO
     NOT FORGET THIS (I'm yelling?).

							matz.