Calling rand using ::dlsym()

dynamic lib failure

#include <iostream>
#include <ffi.h>
#include <dlfcn.h>

int main(int argc, const char* argv[]) {
    char* err_str;
    err_str = ::dlerror();
    if (err_str) {
        std::cout << "dlsym: pre error: " << err_str << "\n";
    }

    void *handle = 0;
    handle = ::dlopen(0,RTLD_LAZY|RTLD_GLOBAL);
    void *fn_ptr = ::dlsym(handle, "rand");
    void (*function)() = reinterpret_cast<void (*)()>(fn_ptr);


    ffi_cif *cif = new ffi_cif;
    uint32_t nargs = 0;
    void *args[nargs];
    int32_t raw_args[nargs];
    for (uint32_t i = 0; i < nargs; i++) {
        args[i] = static_cast<void*>(&raw_args[i]);
    }

    ffi_type rtype = ffi_type_uint32;
    ffi_type **types = new ffi_type*[nargs];

    ffi_status s = ffi_prep_cif(cif, FFI_DEFAULT_ABI, nargs, &rtype, types);
    if (s == FFI_OK) {
        std::cout << "cif: cif is OK\n";
    } else if (s == FFI_BAD_TYPEDEF) {
        std::cout << "cif: One of the ffi_type objects is incorrect\n";
    } else if (s == FFI_BAD_ABI) {
        std::cout << "cif: The abi parameter is invalid\n";
    }

    int value = 0;
    ffi_call(cif, function, &value, args);

    std::cout << "rand val: " << value << "\n";

    err_str = ::dlerror();
    if (err_str) {
        std::cout << "dlsym: post error: " << err_str << "\n";
    }
}