GC - inolen/emscripten GitHub Wiki
Emscripten has support for a Boehm-like API for garbage collection in C/C++ programs. This is useful if your application uses the Boehm API or if you are compiling a language like Java into C/C++ with the goal of then translating it to JavaScript.
API Changes From Boehm
There is no way to run another thread that interrupts the program at intervals in order to GC. So you need to call GC_MAYBE_COLLECT at reasonable intervals, which will do a collection if enough allocations happened since the last one. If you compile to HTML, a timer will be spun for this automatically and you don't need to do anything.
You can also call GC_FORCE_COLLECT which forces a collection. This is useful if there are times in your app when responsiveness is not important (for example, right before starting a new level in a game).
Mechanism
Static allocations are scanned, but the C and JS stacks are not. We can add such scanning at the cost of runtime performance, however, you don't need stack scanning if you compile for browsers and call GC_MAYBE_COLLECT from a setInterval, since the interval will run when there is no relevant C or JS stack to scan (as mentioned before, such a timer will be run for you automatically if you are compiling to HTML).
Pitfalls
The main risk with the current implementation is that we do not force a collection directly from allocations. So if you allocate a lot in between collections, you can run out of memory. You can call GC_FORCE_COLLECT to prevent this in some cases if you know relevant parts in your code.
Relevant Files
system/include/gc.hsrc/library_gc.js