In some cases you have to pass a function pointer to a C function,
i.e., the library wants to call back to your application (and the
pointed-to function is called a callback function). You can pass the
address of an existing C function (that you get with lib-sym,
see Low-Level C Interface Words), but if there is no appropriate C
function, you probably want to define the function as a Forth word.
Then you need to generate a callback as described below:
You can generate C callbacks from Forth code with c-callback.
c-callback ( "forth-name" "{type}" "—" "type" – ) gforth-1.0 “c-callback”
Define a callback instantiator with the given signature. The
callback instantiator forth-name ( xt -- addr ) takes
an xt, and returns the address of the C function
handling that callback.
c-callback-thread ( "forth-name" "{type}" "—" "type" – ) gforth-1.0 “c-callback-thread”
Define a callback instantiator with the given signature. The
callback instantiator forth-name ( xt -- addr ) takes
an xt, and returns the address of the C function
handling that callback. This callback is safe when called from
another thread
This precompiles a number of callback functions (up to the value
callback#). The prototype of the C function is deduced from
its Forth signature. If this is not sufficient, you can add types in
curly braces after the Forth type.
c-callback vector4double: f f f f -- void
c-callback vector4single: f{float} f{float} f{float} f{float} -- void