### Example
##### example.rb
```ruby
h = {}
(1..17).each{h[_1] = _1}
(1..16).each{h.delete(_1)}
h.rehash
```
##### ASAN report
```console
$ bin/mruby example.rb
==52587==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000006998 at pc 0x55a29cddf96b bp 0x7fff7b1b1720 sp 0x7fff7b1b1710
READ of size 4 at 0x602000006998 thread T0
#0 0x55a29cddf96a in ib_it_next /mruby/src/hash.c:639
#1 0x55a29cde2ca2 in ht_rehash /mruby/src/hash.c:900
#2 0x55a29cde379f in h_rehash /mruby/src/hash.c:996
#3 0x55a29cde7f3d in mrb_hash_rehash /mruby/src/hash.c:1735
#4 0x55a29ce77b62 in mrb_vm_exec /mruby/src/vm.c:1451
#5 0x55a29ce5fa88 in mrb_vm_run /mruby/src/vm.c:981
#6 0x55a29ceb87e1 in mrb_top_run /mruby/src/vm.c:2874
#7 0x55a29cf36bdf in mrb_load_exec mrbgems/mruby-compiler/core/parse.y:6805
#8 0x55a29cf36f25 in mrb_load_detect_file_cxt mrbgems/mruby-compiler/core/parse.y:6848
#9 0x55a29cdba0a2 in main /mruby/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c:347
#10 0x7f24ef43b0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
#11 0x55a29cdb4a6d in _start (/mruby/bin/mruby+0x2a3a6d)
0x602000006998 is located 0 bytes to the right of 8-byte region [0x602000006990,0x602000006998)
allocated by thread T0 here:
#0 0x7f24f01cfffe in __interceptor_realloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10dffe)
#1 0x55a29ceb9440 in mrb_default_allocf /mruby/src/state.c:68
#2 0x55a29cdba747 in mrb_realloc_simple /mruby/src/gc.c:228
#3 0x55a29cdba928 in mrb_realloc /mruby/src/gc.c:242
#4 0x55a29cde12e5 in ht_init /mruby/src/hash.c:749
#5 0x55a29cde2b8e in ht_rehash /mruby/src/hash.c:897
#6 0x55a29cde379f in h_rehash /mruby/src/hash.c:996
#7 0x55a29cde7f3d in mrb_hash_rehash /mruby/src/hash.c:1735
#8 0x55a29ce77b62 in mrb_vm_exec /mruby/src/vm.c:1451
#9 0x55a29ce5fa88 in mrb_vm_run /mruby/src/vm.c:981
#10 0x55a29ceb87e1 in mrb_top_run /mruby/src/vm.c:2874
#11 0x55a29cf36bdf in mrb_load_exec mrbgems/mruby-compiler/core/parse.y:6805
#12 0x55a29cf36f25 in mrb_load_detect_file_cxt mrbgems/mruby-compiler/core/parse.y:6848
#13 0x55a29cdba0a2 in main /mruby/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c:347
#14 0x7f24ef43b0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
```
Because if the configuration file didn't contain any `conf.enable_test`, `rake test` would report an exception and exit.
```console
% cat my_config.rb
MRuby::Build.new { toolchain }
% rake MRUBY_CONFIG=my_config.rb test
...SNIP...
rake aborted!
NoMethodError: undefined method `invoke' for nil:NilClass
/var/tmp/mruby/tasks/test.rake:24:in `block (3 levels) in <top (required)>'
Tasks: TOP => test => test:build => test:build:lib
(See full trace by running task with --trace)
```
If the current directory is different from `MRUBY_ROOT` and it has` conf.build_dir` and `conf.enable_cxx_exception` set, it was generating a pathname outside of` build_dir`.
As a result, in some cases files unrelated to mruby could be linked.
```console
% pwd
/tmp/mruby/1/2/3/4/5/6
% mruby_dir=/tmp/mruby/a/b/c/d/mruby
% cat my_config.rb
MRuby::Build.new("host", "build/to/custom/directory") do
toolchain
enable_cxx_exception
end
% rake MRUBY_CONFIG=my_config.rb -f $mruby_dir/Rakefile > logs
% grep CXX logs
CXX a/b/c/d/mruby/src/error-cxx.cxx -> a/b/c/d/mruby/src/error-cxx.o
CXX a/b/c/d/mruby/src/gc-cxx.cxx -> a/b/c/d/mruby/src/gc-cxx.o
CXX a/b/c/d/mruby/src/vm-cxx.cxx -> a/b/c/d/mruby/src/vm-cxx.o
CXX a/b/c/d/mruby/mrbgems/mruby-compiler/core/codegen-cxx.cxx -> a/b/c/d/mruby/mrbgems/mruby-compiler/core/codegen-cxx.o
CXX a/b/c/d/mruby/mrbgems/mruby-compiler/core/y.tab-cxx.cxx -> a/b/c/d/mruby/mrbgems/mruby-compiler/core/y.tab-cxx.o
CXX ../a/b/c/d/mruby/src/error-cxx.cxx -> ../a/b/c/d/mruby/src/error-cxx.o
CXX ../a/b/c/d/mruby/src/gc-cxx.cxx -> ../a/b/c/d/mruby/src/gc-cxx.o
CXX ../a/b/c/d/mruby/src/vm-cxx.cxx -> ../a/b/c/d/mruby/src/vm-cxx.o
```
Prevents the auto-generated mrbc target source code from being compiled under host conditions.
This is because a build error occurred when `conf.enable_cxx_exception` was set.
* Use `_Complex` instead of `complex` (MSYS2 do not support `complex`)
* Use `_Dcomplex` instead of `_Complex` on MSCV
* Avoid operator division and multiplication of complex
### Example
```ruby
begin
throw 1
rescue Exception => e
puts e.message
end
```
#### Before this patch:
```console
$ bin/mruby example.rb
uncaught throw :1
```
#### After this patch (same as Ruby):
```console
$ bin/mruby example.rb
uncaught throw 1
```
This gem uses C99 `_Complex` features. You need a C compiler that
supports `_Complex` to enable this gem. All `gcc`, `clang`, `VC` support
`_Complex` so there should not be a big problem.
`.pi` files are created for `.o` files that `build.products` depends on, but
an error will occur if the build rule is unknown, so add a check.
I don't think this situation would normally arise. However, in
`mattn/mruby-onig-regexp`, when using bundled onigmo, onigmo's `.o` files
are added to dependency of `libmruby.a` in the second and subsequent builds,
and mruby does not know the build rule, so the following error had occured.
```console
rake aborted!
Don't know how to build task '/mruby/build/host/mrbgems/mruby-onig-regexp/onigmo-6.2.0/libonig_objs/ascii.pi' (See the list of available tasks with `rake --tasks`)
```
We have introduced following new instructions.
* `OP_LAMBDA16`
* `OP_BLOCK16`
* `OP_METHOD16`
* `OP_EXEC16`
Each instruction uses 16 bits operand for `reps` index. Since new
instructions are added, `mruby/c` VM should be updated.
Due to new instructions, dump format compatibility is lost, we have
increased `RITE_BINARY_MAJOR_VER`.
In addition, we have decreased the size of `refcnt` in `mrb_irep` from
`uint32_t` to `uint16_t`, which is reasonably big enough.
The `init_SYMBOLS()` function implicitly defined in `MRB_PRESYM_DEFINE_VAR_AND_INITER()` requires some familiarity when trying to find it from the caller.
By introducing `MRB_PRESYM_INIT_SYMBOLS()`, it is possible to find directly from the identifier.
KOBAYASHI Shuji