Mac dylib at runtime

a-mylib.c

// Compile: clang -dynamiclib -Wl,-current_version 1.0 mylib.c -o mylib.dylib
// See it with otool -L mylib.dylib
//mylib.dylib:
//        mylib.dylib (compatibility version 0.0.0, current version 1.0.0)

#include <stdio.h>

__attribute__((constructor))
static void initialize() {
    printf("Initializing MyLib\n");
}

__attribute__((destructor))
static void destroy() {
    printf("Destroying MyLib\n");
}

int printHello()
{
    printf("Hello from MyLib\n");
    return 22;
}

loader.c

#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>

int main (int argc, char *argv[])
{
    void *library = dlopen("mylib.dylib", RTLD_LAZY);

    if (library == NULL)
    {
        const char *error = dlerror();

        fprintf(stderr, "Could not open library\n");

        if (error)
        {
            fprintf(stderr, "Could not open library: %s\n", error);
        }

        exit(EXIT_FAILURE);
    } else {
        void *initializer = dlsym(library, "printHello");

        if (initializer == NULL)
        {
            fprintf(stderr, "Could not find printHello\n");
            exit(EXIT_FAILURE);
        }
        else
        {
            // defines printHelloPtr as a pointer to a function taking void and returning int
            typedef int (*printHelloPtr)(void);
            printHelloPtr init_func = (printHelloPtr)initializer;

            // with no typedef

            /*

            // Define a local variable
            int (*init_func)(void);

            // no need to cast, but if you do, the syntax requires no name in the type
            init_func = (int(*)(void))initializer;
            */

            int result = init_func();

            printf("Got result %i\n", result);
        }
    }

    if (dlclose(library) == -1)
    {
        const char *error = dlerror();

        fprintf(stderr, "Could not close library\n");

        if (error)
        {
            fprintf(stderr, "%s\n", error);
        }

        exit(EXIT_FAILURE);
    }

    return 0;
}