The equal (`==`) method of the comparison target might be redefined
(the root cause of #6262), and not supposed to be compared with NONE.
To reduce chance for the problem, we use `NONE.equal?()` for comparison.
Previously `\x80` was incorrectly mapped to `0`.
```ruby
"\x80\x80\x80\x80".unpack("m*")
# before => "\x00\x00\x00"
# after => ""
```
The reason is that the C string terminator is placed in `base64_dec_tab[128]` and the array length is obtained by `sizeof`.
Therefore, the length of `base64_dec_tab[]` is strictly specified and replaced with element-by-element initialization.
Also, similar changes are made to `base64chars[]`.
the worst case for `Array#reject!` (i.e. a proc always returning `true`)
is at least 5x worse than the worst case for `Array#select!` (proc
always returning `false`)
this commit unifies these implementations and inlines the (effective)
call of `#select!` in `#keep_if` and `#reject!` in `#delete_if`
Immediately frees the call stack and data stack at the end of a non-root fiber.
If the env object needs to be detached, the data stack is reused through `mrb_realloc()`.
Previously, it was not necessary to take into account that `c->cibase` could be `NULL`.
Note that this is no longer the case due to this patch.
In fact, changes to "mruby-fiber" are now required.
This will be a partial merge of #5317 with the following changes.
- Remove `iclass->iv_c` since `iclass->iv_c` is equivalent to `iclass->c`.
- `class_iv_ptr()` returns a single pointer instead of a double pointer.
The old code assumes unary minus (`-@`) does not cause any side effect
(including errors). Considering the code like `-nil; nil`, the
assumption was too aggressive.
Previously, the correct directory could not be obtained in some environments.
Therefore, changed the method to leave an element indicating the parent directory.
fix#6156
The `MRB_TT_BACKTRACE` object has been added for the purpose.
Previously, "use-after-free" could occur because the reference count in `backtrace_location::irep` was not incremented.
fixed#6160
This flag means all the characters in the string can be represented by a
single byte, i.e., the string does not contain any multi-byte character.
Those characters are likely ASCII characters, but may be a part of broken
UTF-8 sequence, so the term 'ASCII' is not sufficient.
Yukihiro "Matz" Matsumoto