From: "Joseph E. Savard" <joseph.savard@...>
Date: 2010-08-11T00:43:30+09:00
Subject: Re: Tail recursion with 1.9

Its commented out. 

See vm_opts.h.

As far as sensing it in Ruby I would think

ruby-1.9.2-rc2.tar.bz2>

Snippet of vm_opts.h below:

#ifndef RUBY_VM_OPTS_H
#define RUBY_VM_OPTS_H

/* Compile options.
 * You can change these options at runtime by VM::CompileOption.
 * Following definitions are default values.
 */

#define OPT_TRACE_INSTRUCTION        1
#define OPT_TAILCALL_OPTIMIZATION    0
#define OPT_PEEPHOLE_OPTIMIZATION    1
#define OPT_SPECIALISED_INSTRUCTION  1
#define OPT_INLINE_CONST_CACHE       1

RUN TIME OPTIONS could be interesting to play with.  You appear to loose the
promise of portability.

See iseq.c (Interesting rb_compile_option_t )

static rb_compile_option_t COMPILE_OPTION_DEFAULT = {
    OPT_INLINE_CONST_CACHE, /* int inline_const_cache; */
    OPT_PEEPHOLE_OPTIMIZATION, /* int peephole_optimization; */
    OPT_TAILCALL_OPTIMIZATION, /* int tailcall_optimization */
    OPT_SPECIALISED_INSTRUCTION, /* int specialized_instruction; */
    OPT_OPERANDS_UNIFICATION, /* int operands_unification; */
    OPT_INSTRUCTIONS_UNIFICATION, /* int instructions_unification; */
    OPT_STACK_CACHING, /* int stack_caching; */
    OPT_TRACE_INSTRUCTION, /* int trace_instruction */
};


   


> From: Iain Barnett <iainspeed@gmail.com>
> Reply-To: <ruby-talk@ruby-lang.org>
> Date: Tue, 10 Aug 2010 23:04:50 +0900
> To: ruby-talk ML <ruby-talk@ruby-lang.org>
> Subject: Tail recursion with 1.9
> 
> Hi,
> 
> I read in the first answer here
> http://stackoverflow.com/questions/824562/does-ruby-perform-tail-call-optimiza
> tion that tail recursion is not on by default and is enabled by uncommenting a
> line in the source before compilation. Is this still true, and is there anyway
> to tell if it's on or not in a particular installation?
> 
> 
> Regards,
> Iain