Hello guys! Can you help me to check how can I track the lifetime of an object loaded in an emscripten app (TS + C++)?
Context: I want to implement a feature where I am trying to reload the app in the same Worker (without killing it). I actually need to destroy all objects inside the this worker. Destroy here can mean to make sure the object is Garbage Collected OR to manually destroys it (if needed - check 3). Basically, I want to implement a shutdown mechanism which is similar with releasing all memory (TS + C++) and check I don't have leaks, like in the C++ world :D. I found few types of objects in my project: 1. “standard” objects: objects created in TS (not C++ related - e.g. no bindings at all) are automatically freed by the GC. This also includes objects created and kept inside C++ using emscpriten::val. Basically 1 is handled by GC. 2. “shared types/objects” + stack allocation: object allocated in C++ on stack and returned to JS. They are automatically GC-ed (be like standard JS objects). 3. “shared types/objects” + heap allocation: e.g. type defined in C++, bind into a TS/JS interface. If in TS I end up using dynamic allocation (a.k.a. new $interface_from_cpp()), I must manually call $object.delete() in JS (check docs <https://emscripten.org/docs/porting/connecting_cpp_and_javascript/embind.html?highlight=memory>: It is strongly recommended that JavaScript code explicitly deletes any C++ object handles it has received. The delete() JavaScript method is provided to manually signal that a C++ object is no longer needed and can be deleted. Both C++ objects constructed from the JavaScript side as well as those returned from C++ methods must be explicitly deleted.). 4. EmscriptenModule-like objects, which from my understanding, will be actually used to load the WASM file intro the browser (?). The lifetime of the EmscriptenModule object is the same as for WASM? (e.g. by releasing all references to the module, will automatically unload the WASM <https://stackoverflow.com/a/56035811/6068071>?) 5. bindings - by actually using EMSCRIPTEN_BINDINGS it seems the runtime creates some global variables (emscripten internal stuff) . They seem to be released when calling atexit ( if this exists (e.g. in a C++ main() -based problem) <https://emscripten.org/docs/getting_started/FAQ.html?highlight=atexit#what-does-exiting-the-runtime-mean-why-don-t-atexit-s-run>: That means that when main() exits, we don’t flush the stdio streams, or call the destructors of global C++ objects, or call atexit callbacks). In my case, I don't have a main() function. I am running in a request frame animation <https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame> based loop. How can I trigger destroying the actual runtime / bindings? Q1: Do you know about any object which is not in {1, 2, 3, 4, 5}? Q2: If 4 is true (destroy module => unload WASM), how can I test this? I don’t really know how to test that works (e.g. check WASM is not present anymore? OR that my operation is a NOP - the module object was GC-ed? and the WASM is still present? ). I didn’t get my answer with Chrome Dev Tools (Memory tab) - maybe I am missing something. Q3: How do I solve 5? :D Unload WASM => destroy bindings? Q4: I know about using Emscripten Sanitizer <https://emscripten.org/docs/debugging/Sanitizers.html> , this is how I discovered that I have memory leaks for bindings. Do you recommend other tools? I also posted this issue on github emscripten [1]. Please let me know if I can give you any other information. Thanks! Best regards, Darius [1] https://github.com/emscripten-core/emscripten/issues/18080 -- You received this message because you are subscribed to the Google Groups "emscripten-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to emscripten-discuss+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/emscripten-discuss/69fb71f8-22e5-494d-856b-c50ad4bb6720n%40googlegroups.com.
