Extern/FFI Concepts

Note

Currently we’re discussing adding a @no_mangle attribute. This would do exactly what it sounds like, it would maintain it’s function name regardless of the name mangling schema.

The extern keyword allows you to use functions from outside KSL. External functions are also the only way to use variadic functions. The extern keyword still needs to be followed by the fn keyword as well as a full function signature.

You can define external functions one by one with this syntax:

extern fn func_in_another_lang_short(bool) -> void;

Or if you need to define a lot of related functions you can use a block syntax instead.

extern {
	fn func_in_another_lang_zero(int) -> void;
	fn func_in_another_lang_one(float) -> int;
	fn func_in_another_lang_two(int) -> float;
}

In order to use variadic functions you can add a ... to the function argument list in the signature. This can only be used for functions defined with extern. Additionally, you can mix the ... alongside other known parameter types. Examples below.

/*
 * This will make an external function definition that can be used in your KSL
 * source code. The `str` means that it expects a string parameter and the `...`
 * means that anything after that is totally up to you.
 *
 * This is a working example to access printf within your KSL program.
 */
extern fn printf(str _, ...) -> void;

extern {
	fn printf(str _, ...) -> void;
	<other_external_function_signatures>
}