The method introduced by #5979 causes a fault by swapping classes.
```console
% bin/mruby -e 'Method = Proc; p Object.method(:inspect)'
zsh: segmentation fault (core dumped) bin/mruby -e 'Method = Proc; p Object.method(:inspect)'
```
After applying this patch, a `TypeError` exception will be raised.
```console
% bin/mruby -e 'Method = Proc; p Object.method(:inspect)'
trace (most recent call last):
[1] -e:1
-e:1:in method: allocation failure of Proc (TypeError)
```
However, if the `mrb_vtype` is the same object, the same care must still be taken as before.
```console
% bin/mruby -e 'Method = Binding; p method(:puts).eval("12345")'
trace (most recent call last):
[1] -e:1
-e:1:in eval: wrong argument type nil (expected Proc) (TypeError)
```
Now all functions with `io_buf` takes `mrb_io_buf` as an argument.
Renamed functions (old names):
- io_init_buf (io_buf_init)
- io_fill_buf (io_buf_fill)
- io_fill_buf_comp (io_buf_fill_comp) for UTF-8 encoding
If `outbuf` is `nil` we allocate a buffer string, if `outbuf` is a
string, we resize it to zero length. In the function `io_read`, this
condition is done twice, so we refactor out to `io_reset_outbuf()`.
I hit the following two problems.
- `io.read(0, buf)` always returned a new empty string object.
- `io.read(num, buf)` was appending data to the given `buf`.
This also meant that `buf` was never empty if EOF was reached.
We count `Proc` upper links then check for upper bounds (default:20),
but now we raise an exception as soon as the count exceeds the limit so
that we can avoid traverse unnecessary upper links.
Since Fiber#to_s did not include location information before #6105,
when location information cannot be retrieved for terminated fibers,
instead of meaningless information such as "(unknown):0", we omit
positional information altogether for terminated fibers; ref #6111
When fiber is terminated, the pointer indicated by `f->cxt->cibase->proc` is not protected from GC.
I should have done this patch way as of commit 9af6264d6b (#6105).
Since `cxt->ci` points to the last active callinfo, `cxt->ci == cxt->cibase`
does not mean it does not have correct `proc` information, so we have
removed the `f->cxt->ci > f->cxt->cibase` check. Instead, just in case
`proc` does not have `irep` information, we try to confirm `proc` does not
point to `CFUNC` nor is not an alias.
It is now possible to specify return destination directly.
This allows callinfo to distinguish between calls to the same proc object.
At the same time, the `Kernel#catch` method is adjusted.
By removing the previously required double lambda object, the REnv object is no longer created as well.
Yukihiro "Matz" Matsumoto