From: Laurent Sansonetti <laurent.sansonetti@...>
Date: 2008-03-15T09:40:15+09:00
Subject: RARRAY_PTR

Hi,

Currently, ruby.h defines RARRAY_PTR as a macro to access the internal
C array of the RArray structure (which represents the Array class).
This macro is used in many places in the Ruby code (and extensions) to
get an element at a particular index

  VALUE v = RARRAY_PTR(ary)[42];

But some people also use it to set values

  RARRAY_PTR(ary)[0] = Qnil;

I think this macro is dangerous because it exposes too much internals.
Also, it is difficult to re-implement RArray using a different storage
structure and efficiently support this macro at the same time. In
MacRuby I am working on a new implementation of the Array class and
will not be able to support this macro for inline modifications.

I therefore suggest to introduce the following macros:

  RARRAY_GET_AT(ary, idx) ...
  RARRAY_SET_AT(ary, idx, value) ...

(The names can be changed of course.)

And start to deprecate RARRAY_PTR.

Thoughts?

RSTRING_PTR is perhaps another case, if people use it to modify the
internal buffer. But as long as it's read-only it's safe I think.

Laurent