mruby-mruby/doc/mruby3.md

User visible changes in mruby3

= New Syntax

We have ported some new syntax from CRuby.

• R-assignment (12 => x)
• Numbered block parameter (x.map{_1 * 2})
• End-less def (def double(x) = x*2)

= Build System

You can specify TARGET option to rake via a command line option, or via an environment variable, e.g.

rake TARGET=host all

or

TARGET=host rake all

It's much easier to switch multiple targets than the previous build_config.rb system.

== presym target

The first compilation of mruby may require generation of a static symbol table named build/presym. You can generate the table by rake gensym.

== target directory

Build target specification files are loaded from target directory. The default TARGET is host which is described in target/host.rb. There are many other targets for example:

• host-gprof: compiles with gprof for performance tuning
• host-m32: compiles in gcc 32bit mode on 64bit platforms
• boxing: compiles all three boxing options
• clang-asan: compiles with clang's Address Sanitizer

target/host.rb comes with comments to help writing a new target description.

If you want to have your target description out of the source tree, you can specify the path to the description file in MRUBY_CONFIG.

= Build Target Contribution

When you write a new target description, please contribute. We welcome your contribution as a GitHub pull-request.

= Configuration Options

Some configuration macro names are changed for consistency

== MRB_USE_METHOD_T_STRUCT

Changed from MRB_METHOD_T_STRUCT.

To use struct version of mrb_method_t. More portable but consumes more memory. Turned on by default on 32bit platforms.