Introduce Ractor mechanism for parallel execution

This commit introduces Ractor mechanism to run Ruby program in
parallel. See doc/ractor.md for more details about Ractor.
See ticket [Feature #17100] to see the implementation details
and discussions.

[Feature #17100]

This commit does not complete the implementation. You can find
many bugs on using Ractor. Also the specification will be changed
so that this feature is experimental. You will see a warning when
you make the first Ractor with `Ractor.new`.

I hope this feature can help programmers from thread-safety issues.

1 files changed, 1 insertions, 1 deletions

diff --git a/variable.h b/variable.h
index ec62023a8b..2f010b6508 100644
--- a/variable.h
+++ b/variable.h
@@ -16,6 +16,6 @@ struct gen_ivtbl {
     VALUE ivptr[FLEX_ARY_LEN];
 };
 
-struct st_table *rb_ivar_generic_ivtbl(void);
+struct st_table *rb_ivar_generic_ivtbl(VALUE obj);
 
 #endif /* RUBY_TOPLEVEL_VARIABLE_H */