tests/custom_messages_proxy.c

/*
 * Copyright 2016 The Emscripten Authors.  All rights reserved.
 * Emscripten is available under two separate licenses, the MIT license and the
 * University of Illinois/NCSA Open Source License.  Both these licenses can be
 * found in the LICENSE file.
 */

#include <emscripten.h>

int main()
{
    EM_ASM({
        customMessageData += '[main]';
        postCustomMessage({ op: 'fromMain' });
    });

    emscripten_exit_with_live_runtime();
    return 0;
}