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Summary of Changes

This pull request adds support for Emscripten to the mruby build system. It includes a new toolchain definition, build configurations for both C and C++ projects, and a fix for a compilation issue in the mruby-cmath gem when compiling with a C++ compiler. The changes aim to allow mruby to be compiled and run in web browsers and other environments supported by Emscripten.

Highlights

Emscripten Toolchain: A new toolchain definition (tasks/toolchains/emscripten.rake) is added, configuring the compiler, linker, and archiver to use Emscripten's tools (emcc, em++, emar). It also sets up compile and link flags, with links to the Emscripten documentation.
Build Configurations: New build configurations (build_config/emscripten.rb and build_config/emscripten-cxx.rb) are added for Emscripten, providing instructions on how to link mruby to Emscripten applications using the mruby-config flags.
C++ Compatibility Fix: A conditional compilation issue in mrbgems/mruby-cmath/src/cmath.c is resolved by adding __EMSCRIPTEN__ to the list of platforms where a specific C++ workaround is needed.

Changelog

Click here to see the changelog

build_config/emscripten-cxx.rb
- Added a new build configuration file for Emscripten C++ projects.
- Includes instructions to use mruby-config flags for compilation and linking (lines 1-5).
- Configures the toolchain to use Emscripten (line 7).
- Enables the C++ ABI (line 11).
build_config/emscripten.rb
- Added a new build configuration file for Emscripten C projects.
- Includes instructions to use mruby-config flags for compilation and linking (lines 1-5).
- Configures the toolchain to use Emscripten (line 7).
mrbgems/mruby-cmath/src/cmath.c
- Modified the conditional compilation directive to include __EMSCRIPTEN__ (line 96).
- This fixes a compilation issue when building with C++ on Emscripten.
tasks/toolchains/emscripten.rake
- Added a new toolchain definition for Emscripten.
- Configures the compiler, linker, and archiver to use Emscripten's tools (lines 18-35).
- Sets up compile and link flags, with links to the Emscripten documentation (lines 4-7).
- Adds -Wno-unused-but-set-variable to compile flags (line 12).

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Trivia time!

What JavaScript engine powers Emscripten, enabling it to run C and C++ code in web browsers?

Click here for the answer
WebAssembly (Wasm) is the technology that allows Emscripten to run C and C++ code in web browsers. It provides a low-level, assembly-like language that can be executed efficiently by modern JavaScript engines.

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