Is there a a way to achieve closures in C

Question

I would like this to work, but it does not:

#include <stdio.h>  typedef struct closure_s {   void (*incrementer) ();   void (*emitter) (); } closure;  closure emit(int in) {    void incrementer() {     in++;   }    void emitter() {     printf("%d\n", in);   }    return (closure) {     incrementer,     emitter   }; }  main() {   closure test[] = {     emit(10),     emit(20)   };    test[0] . incrementer();   test[1] . incrementer();    test[0] . emitter();   test[1] . emitter(); } 

It actually does compile and does work for 1 instance ... but the second one fails. Any idea how to get closures in C?

It would be truly awesome!

Answer 1

Using FFCALL,

#include <callback.h> #include <stdio.h> static void incrementer_(int *in) {     ++*in; } static void emitter_(int *in) {     printf("%d\n", *in); } int main() {     int in1 = 10, in2 = 20;     int (*incrementer1)() = alloc_callback(&incrementer_, &in1);     int (*emitter1)() = alloc_callback(&emitter_, &in1);     int (*incrementer2)() = alloc_callback(&incrementer_, &in2);     int (*emitter2)() = alloc_callback(&emitter_, &in2);     incrementer1();     incrementer2();     emitter1();     emitter2();     free_callback(incrementer1);     free_callback(incrementer2);     free_callback(emitter1);     free_callback(emitter2); } 

But usually in C you end up passing extra arguments around to fake closures.

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Apple has a non-standard extension to C called blocks, which do work much like closures.