The language

Now a::B = c should evaluate a then c.
Anonymous arguments *, **, & can be passed for forwarding.
Multi-precision integer is available now via mruby-bigint gem.

mruby VM and bytecode

OP_ARYDUP was renamed to OP_ARYSPLAT. The instruction name was changed but instruction number and basic behavior have not changed (except that ARYDUP nil makes []).

Tools

mruby

-b only specifies the script is the binary. The files loaded by -r are not affected by the option.
mruby now loads compiled binary if the suffix is .mrb.

mrbc

Add --no-optimize option to disable optimization.

mrbgems

mruby-class-ext

Add Class#subclasses method.
Add Module#undefined_instance_methods method.

New bundled gems

mruby-errno from https://github.com/iij/mruby-errno.git
mruby-set from https://github.com/yui-knk/mruby-set.git
mruby-dir from https://github.com/iij/mruby-dir.git
mruby-data

Breaking Changes

mrb_vm_run() may detach top-level local variables referenced from blocks

When the mrb_vm_run() function (including mrb_top_run()) is called, the previous top-level local variables referenced from blocks is detached under either of the following conditions.

If the stack_keep parameter is given as 0.
If the number of variables in irep to be executed is less than the number of previous top-level local variables.

This change also affects API functions such as mrb_load_string() and mrb_load_file(). The conditions under which the previous top-level local variables referenced from blocks is detached in these functions are as follows:

If the function has no mrbc_context pointer parameter, or the mrbc_context pointer parameter is set to NULL.
If the number of variables held in the mrbc_context pointer is less than the number of previous top-level local variables.

Intentional reliance on previous behavior may cause compatibility problems in your application.

CVEs

Following CVEs are fixed.