From: Jamis Buck <jgb3@...>
Date: 2003-12-30T06:54:50+09:00
Subject: Question about Ruby implementation

I've been poking around the Ruby internals, trying to understand the 
black magic that makes the whole thing run. :)  I think I finally 
understand the garbage collection stuff (and how it determines the roots 
from the stack and registers), but I have a question now about some of 
the macros I've seen:  why do some macros wrap their contents in a "do { 
... } while(0)"?  Is this preferable to simply wrapping them in curly 
braces ("{...}")?  Is it simply a matter of matz's programming style, or 
is there some subtler issue in effect here?

A few macros that do this (for curious persons to reference) are 
JUMP_TAG (in eval.c) and RUBY_CRITICAL (in rubysig.h), though there are 
several others.

Thanks!  (And if there is a more appropriate list for posting questions 
regarding the implementation of Ruby, please direct me there.  Thanks 
again!)

-- 
Jamis Buck
jgb3@email.byu.edu

ruby -h | ruby -e 'a=[];readlines.join.scan(/-(.)\[e|Kk(\S*)|le.l(..)e|#!(\S*)/) {|r| a << r.compact.first };puts "\n>#{a.join(%q/ /)}<\n\n"'