From: Yukihiro Matsumoto <matz@...>
Date: 2005-04-28T00:57:29+09:00
Subject: Re: node.h and nd_line

Hi,

In message "Re: node.h and nd_line"
    on Thu, 28 Apr 2005 00:52:19 +0900, "B. K. Oxley (binkley)" <binkley@alumni.rice.edu> writes:

|#define nd_line(n) ((unsigned int) (((RNODE(n))->flags >> NODE_LSHIFT) & 
|NODE_LMASK))
|#define nd_set_line(n,l) \
|RNODE(n)->flags=((RNODE(n)->flags & ~(-1 << NODE_LSHIFT)) | (((l) & 
|NODE_LMASK) << NODE_LSHIFT))
|
|What is going on?  :)

Line numbers are packed in the flags bits.  It's a trick to save
memory.  Since all nodes and objects shares same heap slot, adding an
extra field cost 4 bytes (or 8 bytes on 64bit machines) for every
object.

							matz.