From: Paul Brannan <pbrannan@...>
Date: 2008-10-22T04:17:10+09:00
Subject: [ruby-core:19425] Re: rb_errinfo() vs rb_rubylevel_errinfo()

On Wed, Oct 22, 2008 at 02:46:56AM +0900, SASADA Koichi wrote:
> How about such an example?
> 
> def m
>   raise Thread.current[:err] = 'bar'
> rescue
> end
> begin
> 
>   raise Thread.current[:err] = 'foo'
> rescue
>   m
>   p $! #=> #<RuntimeError: foo>
>   p Thread.current[:err] #=> "bar"
> end
> 
> BTW, 1.8 also solved such problem.  This shows that 1.8 doesn't use
> thread local variable (TLV) for errinfo (yes, it use TLV, but not
> only TLV).

Yes, 1.8 saves ruby_errinfo on the stack when it evaluates NODE_RESCUE,
then (if not raising a new exception) sets it back when it is done.
YARV looks like it does the same with th->errinfo.

However, on 1.8 ruby_errinfo and $! are always the same, while on YARV
rb_errinfo() may not always be the same as $!.  I found this surprising.

> > Also, I had been curious whether rb_rubylevel_errinfo() should be
> > declared in ruby.h.
> 
> really?  on the trunk?

It is an export symbol that isn't used anywhere inside ruby, so it seems
to be available for users, but I don't see it declared in any of the
public headers.

Paul