memory leak issue

[Anurag9589]

It is very nice for scanning using web assembly and very helpful repository, thanks for sharing.

However, I came across following scenario, please read,
when running demo sample application from iPad, it keeps adding memory and at certain point page gets crashed. It clearly gets noticed in iPad, however in Chrome it shows memory getting increased and after some memory limit, chrome also shows crash behavior.

please suggest or improve the memory management.

[jjhbw]

Hi Anurag, nice find!

I didn't put much thought in testing for memory leaks, so I agree that this is likely a memory leak.

A new wasm buffer is allocated for each new image frame, which is supposed to be destroyed after prediction has finished.

It is possible that this buffer is not freed correctly.
This is the JS code that invokes the buffer freeing method:

barcode-scanner-webassembly/index.html

Lines 91 to 93 in 1ed4d02

	// clean up
	//(this is not really necessary in this example as we could reuse the buffer, but is used to demonstrate how you can manage Wasm heap memory from the js environment)
	api.destroy_buffer(p);

It should call this wasm function, with a pointer to the buffer as an argument.

barcode-scanner-webassembly/scan.c

Lines 72 to 77 in 1ed4d02

	// this function can be used from the javascript environment to free an image buffer.
	EMSCRIPTEN_KEEPALIVE
	void destroy_buffer(uint8_t *p)
	{
	free(p);
	}

Probably something went wrong in invoking this function. Sadly, these bindings are pretty fragile and don't throw errors when something goes wrong.

An alternative, more elegant option would be to re-use the buffer for new frames. This should also improve performance a bit.

I currently dont have time to dive into this, if you find the solution, let me know and i'll merge it in if you want.