From: Eric Wong <normalperson@...>
Date: 2012-05-25T10:21:20+09:00
Subject: Re: [C exten] Could Ruby GC my VALUE in while acquiring the GVL?

I単aki Baz Castillo <ibc@aliax.net> wrote:
> Hi, I'm in C land without GVL and give value to a static VALUE
> variable defined in my .c file and later I acquire the GVL and want to
> use such a VALUE variable:
> 
> 
> // GVL release here:
> 
> static VALUE my_variable;

Static variables in C are global to the process and not on the stack,
so yes, all static VALUEs need to be registered with GC
(rb_global_variable/rb_gc_register_address)

> my_variable = rb_new_str("hello", 5);

rb_str_new() is not safe to call without GVL.

> rb_thread_call_with_gvl(function_with_gvl, NULL);

> So my question is: could Ruby GC my_variable while acquiring the GVL?
> should I keep it from GC by using rb_gc_register_address(&my_variable)

Yeah, Ruby can GC your variables at _any_ time.

Keep in mind rb_global_variable/rb_gc_register_address/rb_new_str/...
all require GVL to function safely (always assume Ruby C API
requires the GVL, only a few C API functions are explicitly marked as
thread-safe).