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

#define SHARED_LIB "sharedlib.so"

int add(int a, int b) { return a + b; }

void test_dlopen_null() {
    void *handle = dlopen(NULL, RTLD_LAZY);
    if (!handle) {
        printf("dlopen(NULL) failed: %s\n", dlerror());
        exit(1);
    }

    int (*f)(int, int);
    *(void **)(&f) = dlsym(handle, "add");

    if (!f) {
        printf("dlsym(handle, add) failed: %s\n", dlerror());
        exit(2);
    }
    int a = 22;
    int b = 33;
    printf("add(%d, %d) = %d\n", a, b, f(a, b));
    dlclose(handle);
}

void test_dlopen_libc() {
    void *handle = dlopen("libc.so.6", RTLD_LAZY);
    if (!handle) {
        printf("dlopen(libc.so.6) failed\n");
        exit(1);
    }

    int (*f)(const char *);
    *(void **)(&f) = dlsym(handle, "puts");

    if (!f) {
        printf("dlsym(handle, puts) failed\n");
        exit(2);
    }
    f("puts from dlopened libc");
    dlclose(handle);
}

void test_dlsym_function() {
    void *handle = dlopen(SHARED_LIB, RTLD_LAZY);
    if (!handle) {
        printf("dlopen(sharedlib.so) failed\n");
        exit(1);
    }

    void (*f)();
    *(void **)(&f) = dlsym(handle, "print");

    if (!f) {
        printf("dlsym(handle, print) failed\n");
        exit(2);
    }
    f();
    dlclose(handle);
}

void test_dlsym_global_var() {
    void *handle = dlopen(SHARED_LIB, RTLD_LAZY);
    if (!handle) {
        printf("dlopen(sharedlib.so) failed\n");
        exit(1);
    }
    int *global_var = dlsym(handle, "global_var");
    if (!global_var) {
        printf("dlsym(handle, global_var) failed\n");
        exit(2);
    }
    printf("main: global_var == %d\n", *global_var);
    dlclose(handle);
}

void test_dlsym_tls_var() {
    void *handle = dlopen(SHARED_LIB, RTLD_LAZY);
    if (!handle) {
        printf("dlopen(sharedlib.so) failed\n");
        exit(1);
    }
    int *tls_var = dlsym(handle, "tls_var");
    if (!tls_var) {
        printf("dlsym(handle, tls_var) failed\n");
        exit(2);
    }
    printf("main: tls_var == %d\n", *tls_var);
    dlclose(handle);
}

void test_dlunload(void) {
    void *handle = dlopen(SHARED_LIB, RTLD_LAZY | RTLD_LOCAL);
    void *handle2 = dlopen(SHARED_LIB, RTLD_LAZY | RTLD_LOCAL);
    assert(handle == handle2 && handle);
    assert(!dlclose(handle));
    void *handle3 = dlopen(SHARED_LIB, RTLD_LAZY | RTLD_NOLOAD);
    assert(handle3 == handle2);
    assert(!dlclose(handle3));
    assert(!dlclose(handle2));
    void *handle4 = dlopen(SHARED_LIB, RTLD_LAZY | RTLD_NOLOAD);
    assert(handle4 == NULL);

    void *handle5 = dlopen(SHARED_LIB, RTLD_LAZY | RTLD_GLOBAL);
    assert(handle5);
    assert(!dlclose(handle5));
    void *handle6 = dlopen(SHARED_LIB, RTLD_LAZY | RTLD_NOLOAD);
    assert(handle6 == NULL);
}

int main() {
    test_dlopen_null();
    test_dlopen_libc();
    test_dlsym_function();
    test_dlsym_global_var();
    test_dlsym_tls_var();
    test_dlunload();
}