Add dynamic tracing system to JS library code This system is designed to replace all the existing compile time DEBUG settings (SYSCALL_DEBUG, GL_DEBUG, FS_DEBUG, etc) with a system where the channels can be enabled/disabled at runtime. The old settings till work and enable the respective channel at startup. Under node channels can be enabled by running with EM_DEBUG set in the environment. This is a comma separated list of channel names. Fixes: #15057
Main project page: https://emscripten.org
GitHub CI status: 
Chromium builder status: emscripten-releases
Emscripten compiles C and C++ to WebAssembly using LLVM and Binaryen. Emscripten output can run on the Web, in Node.js, and in wasm runtimes.
Emscripten provides Web support for popular portable APIs such as OpenGL and SDL2, allowing complex graphical native applications to be ported, such as the Unity game engine and Google Earth. It can probably port your codebase, too!
While Emscripten mostly focuses on compiling C and C++ using Clang, it can be integrated with other LLVM-using compilers (for example, Rust has Emscripten integration, with the wasm32-unknown-emscripten and asmjs-unknown-emscripten targets).
Emscripten is available under 2 licenses, the MIT license and the University of Illinois/NCSA Open Source License.
Both are permissive open source licenses, with little if any practical difference between them.
The reason for offering both is that (1) the MIT license is well-known and suitable for a compiler toolchain, while (2) LLVM‘s original license, the University of Illinois/NCSA Open Source License, was also offered to allow Emscripten’s code to be integrated upstream into LLVM. The second reason became less important after Emscripten switched to the LLVM wasm backend, at which point there isn't any code we expect to move back and forth between the projects; also, LLVM relicensed to Apache 2.0 + exceptions meanwhile. In practice you can just consider Emscripten as MIT licensed (which allows you to do pretty much anything you want with a compiler, including commercial and non-commercial use).
See LICENSE for the full content of the licenses.