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routines for creating typesafe generic containers


Rusty Russell <[email protected]>


This code lets users create a structure with a typecanary; your API is then a set of macros which check the type canary before calling the generic routines.


#include <ccan/tcon/tcon.h>
#include <stdio.h>

// A simple container class.  Can only contain one thing though!
struct container {
        void *contents;
static inline void container_add_raw(struct container *c, void *p)
        c->contents = p;
static inline void *container_get_raw(struct container *c)
        return c->contents;

// This lets the user define their container type; includes a
// "type canary" to check types against.
        struct name { struct container raw; TCON(type canary); }

// These macros make sure the container type and pointer match.
#define container_add(c, p) \
        container_add_raw(&tcon_check((c), canary, (p))->raw, (p))
#define container_get(c) \
        tcon_cast((c), canary, container_get_raw(&(c)->raw))

// Now, let's define two different containers.
DEFINE_TYPED_CONTAINER_STRUCT(int_container, int *);
DEFINE_TYPED_CONTAINER_STRUCT(string_container, char *);

int main(int argc, char *argv[])
        struct int_container ic;
        struct string_container sc;

        // We would get a warning if we used the wrong types...
        container_add(&ic, &argc);
        container_add(&sc, argv[argc-1]);

        printf("Last arg is %s of %i arguments\n",
               container_get(&sc), *container_get(&ic) - 1);
        return 0;
// Given "foo" outputs "Last arg is foo of 1 arguments\n"
// Given "foo bar" outputs "Last arg is bar of 2 arguments\n"


CC0 (Public domain)