Unusual Multithreading API

[HumanBodyMacAndCheese]

Just downloaded and built JerryScript yesterday and noticed something odd about running multiple contexts. According to my reading in the documentation, it says that you have to manually switch the currently running contexts if compiled with external contexts enabled. Is there a more ergonomic way to use different contexts* or is this engine mainly single-threaded? If not, then is it due to memory constraints?

• I mean like using a different thread like a separate object:
  • duk_context* ctx = duk_create_heap_default(); // Duktape allows use of contexts like this, and it's also usable for microcontrollers.
  • lua_State* L = luaL_newstate(); // Ditto, but for Lua and LuaJIT.

[markand]

It has been designed for microcontrollers in mind where multiple context doesn't really matter. It has nothing to do with multi threading, neither Lua nor Duktape are thread safe on their own. Maybe you refer to reentrancy.

With external context enabled you must implement three functions and your own way to indicate jerryscript which context is currently active.

Basically something like:

static MyObject *my_current_object;

size_t
jerry_port_context_alloc(size_t context_size)
{
    // increase context size if you need
    context_size = 1024*1024;

    // store the allocated context inside your current object.
    my_current_object->ctx = calloc(1, context_size);

    return my_current_object->ctx;
}

struct jerry_context_t *
jerry_port_context_get(void)
{
	return my_current_context;
}

void
jerry_port_context_free(void)
{
	free(my_current_context);
}

Then when you want to create a new context you will:

1. Create my_current_object as you may need
2. Call jerry_init() which will invoke jerry_port_context_alloc
3. Then use any jerryscript API function

Finally, if you need another context. Before calling any of the jerryscript function, make sure that my_current_object points to the appropriate user object. Basically your code will look like:

my_current_object = &object_a;
jerry_object(...);
jerry_set_property_sz(...);
my_current_object = NULL;