Now the method tables (in classes/modules and caches) keeps C function
pointers without wrapping in `struct RProc` objects. For the sake of
portability, `mrb_method_t` is represented by the struct and union, but
if the most significant bit of the pointer is not used by the platform,
`mrb_method_t` should be packed in `uintptr_t` to reduce memory usage.
`MRB_METHOD_TABLE_INLINE` is turned on by default for linux.
Make `block_given?` to search for the top of the scope first.
The top of the scope means either:
* the top method body
* the enclosing class body
* the top-level
The special case is the method defined by `define_method` with a
block as in #3841. In cases like this, the method body (given by
a block) is not considered as the top of the scope. You need to use
`&block` in the block parameter if you want to know if a block is
given to the method.
This commit also changes the behavior of `MRB_PROC_SCOPE` flag.
Now it is only set if the `proc` is either a class body or a method
body defined in Ruby. It is no longer set for a block that given to
`define_method`.
When `block_given?` is called from a block given to `define_method`
as a method body, the `bidx` may not be within `env` saved closure.
In this case, it causes heap buffer overflow.
Instead of `irep` links, we added a `upper` link to `struct RProc`.
To make a space for the `upper` link, we moved `target_class` reference.
If a `Proc` does not have `env`, `target_class` is saved in an `union`
shared with `env` (if a `Proc` has env, you can tell it by `MRB_PROC_ENV_P()).
Otherwise `target_class` is referenced from `env->c`. We removed links
in `env` as well.
This change removes 2 members from `mrb_irep` struct, thus saving 2
words per method/proc/block. This also fixes potential memory leaks
due to the circular references caused by a link from `mrb_irep`.
Instead of `irep -> proc` chain, we use `irep -> irep` chain to
avoid GC bugs like #3804. We added `target_class` reference to
`mrb_irep` struct. That means one more word consumption per `irep`.
Instead of preserving a backtrace in `mrb_state`, `mrb_exc_set`
keeps packed backtrace in an exception object. `#backtrace` unpacks
it to an array of strings.
Calling `mrb_funcall()` and `mrb_yield()` (and their related
functions) are discouraged unless absolutely necessary, because
it can cause this kind of issues very easily.
Inline structures have no instance variables, no finalizer, and offer as much space as possible in RBASIC object. This means 24 bytes on 64-bit platforms and 12 bytes on 32-bit platforms.
mruby-inline-struct gem is only provided for testing.
Yukihiro "Matz" Matsumoto