From: matz@... (Yukihiro Matsumoto)
Date: 2003-01-23T12:16:34+09:00
Subject: Re: Ruby, C, and garbage collection

Hi,

In message "Ruby, C, and garbage collection"
    on 03/01/23, Tomasz Wegrzanowski <taw@users.sf.net> writes:

|    VALUE a, b, c;
|
|    a = rb_some_function_1();
|    b = rb_some_function_2();
|    c = rb_do_something(a,b);
|
|In this code, if Ruby decides to do GC during rb_some_function_2,
|`a' will be destroyed, and it will segfault at rb_do_something.

I don't think so.  Ruby uses conservative GC, which scans C stack
region to protect Ruby object reference, so that an object referred
from the variable a is not destroyed.

But in some cases, local variables may vanish before function
terminates, for example:

  VALUE a;
  char *p

  a = function_returns_string();
  p = RSTRING(a)->ptr;
  ... process goes on referring p, but no a ...

in such cases, an object referred from a might be reclaimed.
For a workaround, you can declare a as

  volatile VALUE a;

to turn off too much optimization.

							matz.