plugin

dlopen.c

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

const int (*foo_pointer)(void);

int main(int argc, char *argv[])
{
	void *handle = NULL;
	char *error = NULL;

	if (argc != 2)
		return 1;

	handle = dlopen(argv[1], RTLD_NOW);
	if (!handle) {
		printf ("dlopen failed: %s\n", dlerror());
		return 1;
	}

	foo_pointer = dlsym(handle, "foo");
	error = dlerror();
	if (error) {
		printf("dlsym failed: %s\n", error);
		dlclose(handle);
		return 1;
	}

	printf ("foo returns: %d\n", (*foo_pointer)());

	dlclose(handle);
	return 0;
}

foo1.c

#include <stdio.h>

extern int foo ();

int main ()
{
        printf ("%d\n", foo ());

        return 0;
}

foo2.c

extern int foo ();

int bar ()
{
        return foo ();
}

foo3.c

int foo ()
{
        return 42;
}

Makefile

# dlopen test

CC	= gcc
RM	= rm -fr

SRC	= foo1.c foo2.c foo3.c
OBJ	= $(SRC:.c=.o)
OUT	= foo1 foo2.so foo3.so dlopen

CFLAGS	+= -g
CFLAGS	+= -fPIC

all:	$(SRC) $(OBJ) $(OUT)

.c.o:
	$(CC) $(CFLAGS) -c $< -o $@

foo1:	foo1.o foo2.so foo3.so
	$(CC) -o $@ foo1.o foo2.so foo3.so

foo2.so:	foo2.o foo3.so
	$(CC) -shared -o foo2.so foo2.o foo3.so

foo3.so:	foo3.o
	$(CC) -shared -o foo3.so foo3.o

clean:
	$(RM) foo[123].o
	$(RM) foo[23].so
	$(RM) foo1 dlopen

dlopen:	dlopen.c
	$(CC) -o $@ dlopen.c -ldl

run:	foo1 dlopen foo3.so
	LD_LIBRARY_PATH=. foo1
	LD_LIBRARY_PATH=. dlopen foo3.so