If you come across a C function pointer (e.g., in some C-constructed
structure) and want to call it from your Forth program, you could use
the structures as described above by defining a macro. Or you use
c-funptr.
c-funptr ( "forth-name" <{>"c-typecast"<}> "{type}" "—" "type" – ) gforth-1.0 “c-funptr”
Define a Forth word forth-name. Forth-name has the
specified stack effect plus the called pointer on top of stack,
i.e. ( {type} ptr -- type ) and calls the C function
pointer ptr using the typecast or struct access
c-typecast.
Let us assume that there is a C function pointer type func1
defined in some header file func1.h, and you know that these
functions take one integer argument and return an integer result; and
you want to call functions through such pointers. Just define
\c #include <func1.h>
c-funptr call-func1 {((func1)ptr)} n -- n
and then you can call a function pointed to by, say func1a as
follows:
-5 func1a call-func1 .
The Forth word call-func1 is similar to execute, except
that it takes a C func1 pointer instead of a Forth execution
token, and it is specific to func1 pointers. For each type of
function pointer you want to call from Forth, you have to define
a separate calling word.