Dynamic reloading PoC

first.c

#include <stdio.h>
#include <stdbool.h>

bool hello(void)
{
  if (printf("Hello first\n") < 0)
    return false;
  return true;
}

Makefile

CC	= gcc

CFLAGS	= -Wall -Wextra -std=gnu99

LDFLAGS	= -ldl

RM	= rm -f

poc: poc.o first.so second.so

first.so: first.c
	$(CC) $(CFLAGS) -shared -fPIC -o $@ $^

second.so: second.c
	$(CC) $(CFLAGS) -shared -fPIC -o $@ $^

fclean:
	$(RM) first.so second.so poc.o poc

re: fclean poc

poc.c

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

#define ERROR(NAME) ({ perror(NAME); false; })

typedef bool (*t_hellofunc)(void);

static bool callhello(void *handle)
{
  t_hellofunc hello = NULL;

  hello = dlsym(handle, "hello");

  if (hello == NULL)
    return ERROR("dlsym");

  return hello();
}

static bool poc(const char *library)
{
  bool ret = true;
  void *handle = NULL;

  handle = dlopen(library, RTLD_LAZY);
  if (handle == NULL)
    return ERROR("dlopen");

  ret = callhello(handle);

  if (dlclose(handle) != 0)
    return ERROR("dlclose");

  return ret;
}

int main(void)
{
  if (!poc("first.so"))
    return EXIT_FAILURE;

  if (!poc("second.so"))
    return EXIT_FAILURE;
  return EXIT_SUCCESS;
}

second.c

#include <stdio.h>
#include <stdbool.h>

bool hello(void)
{
  if (printf("Hello second\n") < 0)
    return false;
  return true;
}