JS to C

A compiled implementation of ES5, targetting C. I've finished the project as it now supports the parts of the language I found most interesting for a compiled implementation:

• ✅ closures
• ✅ garbage collection
• ✅ exceptions
• ✅ event based IO
• ✅ object system - prototypes etc

Read my notes for a rough dev notes, or read more polished write ups on my blog.

Next thing to do - see TODO.md.

Example

The following JS

function fact(n) {
    return n < 3 ? n : n * fact(n - 1);
}
console.log(fact(5));

outputs as a C program. For instance the compiled fact function looks like:

// ...
JsValue *fact_1(Env *env) {
  JsValue *return_2;
  JsValue *left_5 = (envGet(env, interned_7) /* n */);
  JsValue *right_6 = (jsValueCreateNumber(3));
  JsValue *conditionalPredicate_4 = (LTOperator(left_5, right_6));
  JsValue *conditionalValue_3;
  if (isTruthy(conditionalPredicate_4)) {
    return_2 = (envGet(env, interned_7) /* n */);
  } else {
    JsValue *left_8 = (envGet(env, interned_7) /* n */);
    JsValue *callee_10 = (envGet(env, interned_11) /* fact */);
    JsValue *left_12 = (envGet(env, interned_7) /* n */);
    JsValue *right_13 = (jsValueCreateNumber(1));
    JsValue *call10Arg_0 = (subtractOperator(left_12, right_13));
    JsValue *args_10[] = {call10Arg_0};
    JsValue *right_9 = (functionRunWithArguments(callee_10, env, args_10, 1));
    return_2 = (multiplyOperator(left_8, right_9));
  }
  return return_2;
}
// ...

Guide

./runtime
    the C implementation of the language runtime
./src
    the TypeScript compiler

Testing

Functional

Run npm test to run/update tests. ./scripts/test-by-name $name to run a single test.

Failed tests provide a command to compile and run the C program with the debugger.

Unit

The runtime has unit tests - use the make test in ./runtime to run them, and ./runtime/scripts/compile-test-loop test-file-basename.

Runtime

Runtime C libraries for js-to-c.

Installing

Dependencies:

• clang
• Make
• CMake (for libuv)

I'm trying to limit my focus to learning about compilation, so I've made no attempt to make this cross platform. It shouldn't be too tricky, libuv is the big dependency and it's cross platform.

make install

Developing

Builds and runs all tests:

make test

Libraries

See lib - currently just

• debug.h
  • debug macros

Dynamic libraries

The runtime is built into a dynamic library to avoid recompiling. There's also a prelude, which allows langauge features to be implemented in JS that's pre-compiled to C.

Runtime

Files prefixed _ are private to the runtime and should not be relied on.

Potential issues

grep for HMM to see potential problems I'm leaving alone for now as they seem tricky to solve properly/I'm unsure they'll be a problem in practice. Good place to look if weird bugs occur.