Executable Linux shared library

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

const char interp[] __attribute__((section(".interp"))) = "/lib64/ld-linux-x86-64.so.2";

void test() {
        printf("test\r\n");
}

extern "C" void _main(int argc, char **argv) {
        printf("main\r\n");
        test();
        exit(0);
}

user@user-Aspire-4530 ~/DEV $ g++ -shared -fPIC -o libtest.so libtest.c -Wl,-e,_main
user@user-Aspire-4530 ~/DEV $ LD_PRELOAD=./libtest.so ls
libtest.c  libtest.o  libtest.so
user@user-Aspire-4530 ~/DEV $ ./libtest.so 
main
test
user@user-Aspire-4530 ~/DEV $ readelf -l /bin/ls | grep interpreter