If `mrb->jmp` is `NULL` and the function `mrb_funcall_with_block()` is
called, GC Arena is returned from the function with over-used.
- A normal (no global exodus) return will consume two GC Arena's.
- In the event of an exception, five GC Arena are consumed.
This patch reduces consumption in both cases to one.
Differences from the PR #4940:
* Use simple search for short strings only.
* "short" means `m+n` is shorter than `MRB_QS_SHORT_STRING_LENGTH`.
* The current default value for `MRB_QS_SHORT_STRING_LENGTH` is 2048.
The basic idea of this change is from @dearblue.
Note: the arguments of `mrb_str_pool()` have changed, but the function
is provided for internal use (No `MRB_API`). So basically you don't have
to worry about the change.
Because literal pool may be released by GC.
#### Example:
```ruby
s1 = eval('"abcdefghijklmnopqrstuvwxyz01"')
GC.start
p s1 #=> "\x00\x00\x00\x00\x00\x00\x00\x90\x00\x00\x00\x00\x00\x00\x00\x90\x03\x00stuvwxyz01"
```
#### Example (with `MRB_METHOD_CACHE`)
```ruby
GC.start
c = Class.new
p c #=> #<Class:0x7fd6a180e790>
c.new #=> cache `c.new`
c = nil
GC.start #=> `c` is GCed
r = Range.dup
p r #=> #<Class:0x7fd6a180e790>
# [same pointer as `c`]
r.new(2, 3) #=> ArgumentError: 'initialize':
# wrong number of arguments (2 for 0)
# [`c.new` is called instead of `r.new`]
```
#### Cause
An entry of method cache is identified by class pointer and method
id. However, reusing memory after GC may create a class with the same
pointer as the cached class.
#### Treatment
Cleared method caches of the class when the class is GCed.
The following improvements are made according to Ruby's behavior:
- Match location number to index.
- Remove duplicate most recent call output.
- Fix that first call is not output when array (unpacked) backtrace.
### Example
```ruby
def a; raise "error!" end
def b; a end
begin
b
rescue => e
e.backtrace if ARGV[0] == "unpack" # unpack backtrace
raise e
end
```
#### Before this patch:
```
$ bin/mruby example.rb unpack
trace (most recent call last):
[0] example.rb:2:in b
[1] example.rb:1:in a
example.rb:1: error! (RuntimeError)
```
#### After this patch:
```
$ bin/mruby example.rb unpack
trace (most recent call last):
[2] example.rb:4
[1] example.rb:2:in b
example.rb:1:in a: error! (RuntimeError)
```
Because location info (file name and line number) is kept in the backtrace,
it should not be kept in the result of `inspect` (and the exception object
itself), I think.
### Example
```ruby
# example.rb
begin
raise "err"
rescue => e
p e
end
```
#### Before this patch:
```
$ bin/mruby example.rb
example.rb:2: err (RuntimeError)
```
#### After this patch:
```
$ bin/mruby example.rb
err (RuntimeError)
```
#### Before this patch:
```
$ mruby -e '[].each(1){}' #=> no error
```
#### After this patch:
```
$ mruby -e '[].each(1){}' #=> ArgumentError: wrong number of arguments
```
Consecutive `_` is not allowed as a numeric expression:
1_2__3 #=> SyntaxError
Float("1_2__3") #=> ArgumentError
Integer("1_2__3") #=> ArgumentError
"1_2__3".to_i #=> 12
But `String#to_f` accept it, so I fixed the issue.
Before this patch:
"1_2__3".to_f #=> 123
After this patch:
"1_2__3".to_f #=> 12
If ":" is after "|" and there is no "?" or "*", the keyword argument
could not be obtained and it was not initialized with `undef`.
For example: "|oo:"
* The allocated memory is guaranteed to be aligned for any data type (it was
not guaranteed when string type is embed).
* Make allocation size exactly specified size (does not allocate space for a
null byte).
Yukihiro "Matz" Matsumoto