From: Iain Barnett <iainspeed@...>
Date: 2010-08-13T06:52:45+09:00
Subject: Re: Tail recursion with 1.9




On 10 Aug 2010, at 16:43, Joseph E. Savard wrote:

> 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 */
> };
> 

Thanks for the reply. Finally got 1.9.1-p429 to compile, and I set  #define OPT_TAILCALL_OPTIMIZATION   1  before compiling, which hopefully is right, I don't know C.

Do you know any way I can check it's definitely on, aside from attempting to blow the stack with something hugely recursive?

Iain