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.
#### 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.
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)
```
Previously, `mrb_int` was used as the type that represents the buffer size
on memory, but the sizes of `RString` and `RArray` exceed 6 words when
`MRB_INT64` is enabled on 32-bit CPU.
I don't think it is necessary to be able to represent the buffer size on
memory that exceeds the virtual address space. Therefore, for this purpose,
introduce `mrb_ssize` which doesn't exceed the sizes of `mrb_int` and
pointer.
I think all `mrb_int` used for this purpose should be changed to
`mrb_ssize`, but currently only the members of the structures (`RString`,
`mrb_shared_string`, `RArray` and `mrb_shared_array`) are changed.
The default implementations of type predicate macros use `mrb_type`.
But `mrb_type` with `MRB_WORD_BOXING` isn't very efficient, so the new
implementations avoid `mrb_type`.
In lld linked programs, .rodata comes before .text, thus mrb_ro_data_p
will return false for strings in .rodata. Change the lower bound from
_etext to __ehdr_start to catch these cases. This works for ld.bfd, gold
and lld, and it does not have false positives even if .init_array does
not exist.
Remove the branch that uses _edata: strings in .data can be modified so
this is semantically incorrect. Delete the __APPLE__ branch (its
manpages say get_etext() and get_edata() are strongly discouraged).
.init_array has been adopted by most ELF platforms to supersede .ctors.
Neither _etext nor _edata is used, so rename MRB_USE_ETEXT_EDATA to
MRB_USE_EHDR_START.
`MRB_METHOD_TABLE_INLINE` was fragile. It requires `-falign-functions=n`.
On platform that uses higher bits of function pointers, you can use new
`MRB_METHOD_T_STRUCT` configuration macro.
So you don't need `-falign-functions=2` anymore. Instead your platform
must not use higher bits of the pointer (true for most platforms).
If not, you have to use `struct mrb_method_t` version.
The changes at b2c3d88f were inappropriate because the memory layout of bit
fields are implementation defined. Therefor, I fixed it not to use bit
fields.
The default implementation of `mrb_immediate_p` uses `mrb_type`. However,
in `MRB_WORD_BOXING`, `mrb_type` has many branches and is inefficient, so
provide an implementation that does not use `mrb_type`.
On 64-bit CPU, there is padding in `RBasic`, so reorder the fields and use
it as buffer of embedded string. This change allows 4 more bytes to be
embedded on 64-bit CPU.
However, an incompatibility will occur if `RString::as::ary` is accessed
directly because `RString` structure has changed.
When building WebAssembly targets with clang (e.g. wasm32-unknown-unknown), all
symbols are hidden by default. To export a symbol, it must be marked with
__attribute__((visibility(default)))
Rather than detecting this exotic target in mruby, allow MRB_API to be defined
externally.
Hiroshi Mimaki