Re: cell

[Masao Uebayashi]

> The manual is not quite up-to-date wrt cells.  It's right that most
> objects have a two-word header, but in the meantime so-called `double
> cells' have been introduced, which are four-word cells.  They are used
> for some data types (such as real numbers IIRC) to avoid an extra
> memory reference when accessing the data portion of an object.

Hmm. I imagined, by reading the section 33.2.2 of the reference, that
`a table of heap segment' is throughly aligned by two words like this:

     a table of heap segment
 --------------------------------
 |                              |
 |       |_:_|_:_|              |
 |       |_:_|_:_|              |
 |       |_:_|_:_|              |
 |                              |
 |       |___|___| <--- a cell  |
 |                              |
 |       |___|___|              |
 |       |___|_----> (...)      |
 |       |___|___|              |
 |       |___|_----------> (...)|
 |       |___|___|              |
 |       |___|___|              |
 |       |_:_|_:_|              |
 |       |_:_|_:_|              |
 |       |_:_|_:_|              |
 |     -->   <--                |
 |       word (usually 32bit)   |
 |                              |
 --------------------------------

If four-word cells were introduced, all the tables are aligned by four
words?

TIA, M

---
Masao Uebayashi <address@hidden>    --- We like raw eggs.