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Exceptions are used in OpenCascade to handle certain types of errors. OpenCascade.js uses Emscripten's non-native exception implementation to allow JavaScript code to handle exceptions that were thrown from C++ / WebAssembly. Emscripten's non-native implementation is well supported on all major browsers and runtimes but comes with the drawback of greatly increased file size and a performance penalty. Native WebAssembly exceptions will improve this, but are not yet well supported in common browsers and runtimes.

Check out the WebAssembly Roadmap... to track the progress of new WebAssembly features.