From: Ian Leitch <port001@...>
Date: 2009-07-14T07:44:46+09:00
Subject: Re: rb_eval_string blocks on loops even if run inside a thread.

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Thanks,

I did think of using pthreads, though the code I need to eval will regularly
touch any number of existing objects so I don't think there's a way to stay
safe using pthreads. Do you know how to spawn a ruby green thread in C?

2009/7/13 <brabuhr@gmail.com>

> On 7/13/09, Ian Leitch <port001@gmail.com> wrote:
> > I'm trying to use rb_eval_string to execute a bunch of code and return
> from
> > it straight away. My problem is that the code I want to eval contains a
> > continuous loop. Even if I wrap the code in a thread the call still
> blocks
> > due to the loop. Note that I don't get the same behaviour when using
> eval()
> > outside of the C API.
> >
> > E.g:
> >
> > rb_eval_string("Thread.new { loop { puts 1; sleep 0.2 }}"); <-- blocks
> > eval("Thread.new { loop { puts 1; sleep 0.2 }}") <--- doesn't block
> >
> > My guess is to spawn a ruby thread in C and call rb_eval_string inside
> that,
> > I can't find any examples of using the thread functions on google though
> so
> > I'm a bit stuck. Could someone give me a few pointers or perhaps some
> > example code?
>
> This is the first time I have ever tried embedding Ruby in C, but I
> hope it helps.  (The idea is to run ruby from a C thread so the rest
> of your C program can maybe run in parallel):
>
>
> #include <ruby.h>
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <pthread.h>
>
> void *do_ruby(void* param)
> {
>  ruby_init();
>  rb_eval_string("loop { puts 'hello from ruby world'; sleep 5 }");
>  ruby_finalize();
> }
>
> int main(int argc, char *argv[])
> {
>  pthread_t ruby_thread;
>
>  printf("BEFORE DO_RUBY\n");
>
>  pthread_create( &ruby_thread, NULL, do_ruby, NULL);
>
>  printf("AFTER DO_RUBY\n");
>
>  pthread_join(ruby_thread, NULL);
>
>  return 0;
> }
>
>
> > gcc -o foo -lpthread -lruby1.8 -I/usr/lib/ruby/1.8/i486-linux foo.c
> > ./foo
> BEFORE DO_RUBY
> hello from ruby world
> AFTER DO_RUBY
> hello from ruby world
> hello from ruby world
> ^C(eval): (eval):0:in `sleep':  (Interrupt)
>        from (eval):0
>        from (eval):0:in `loop'
>        from (eval):0
> (eval): [BUG] Segmentation fault
> ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]
>
> Abort
>
>
> But, be aware:
> "ruby is not thread-safe. If you embed ruby into a multi-threaded
> application then you will need to semaphore protect all access to
> ruby. Warning: Insufficient semaphore protection can be hard
> debuggable." [1]
>
> [1] http://metaeditor.sourceforge.net/embed/#id2842564
>
>

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