How to create a real thread using clone () on Linux?

I am trying to create a new thread using clone () . With the following code (...):

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

#define _SCHED_H 1
#define __USE_GNU 1
#include <bits/sched.h>

#define STACK_SIZE 4096

int func(void *arg) {
    printf("Inside func.\n");
    sleep(1);
    printf("Terminating func...\n");

    return 0;
}

int main() {
    printf("This process pid: %u\n", getpid());
    char status_file[] = "/proc/self/status";
    void *child_stack = malloc(STACK_SIZE);
    int thread_pid;

    printf("Creating new thread...\n");
    thread_pid = clone(&func, child_stack+STACK_SIZE, CLONE_SIGHAND|CLONE_FS|CLONE_VM|CLONE_FILES, NULL);
    printf("Done! Thread pid: %d\n", thread_pid);

    FILE *fp = fopen(status_file, "rb");

    printf("Looking into %s...\n", status_file);

    while(1) {
        char ch = fgetc(fp);
        if(feof(fp)) break;
        printf("%c", ch);
    }

    fclose(fp);

    getchar();

    return 0;
}

I get the following:

This process pid: 10839
Creating new thread...
Done! Thread pid: 10840
Inside func.
Looking into /proc/self/status...
Name:   threadTest02
State:  R (running)
Tgid:   10839
Pid:    10839
PPid:   4777
TracerPid:      0
Uid:    1000    1000    1000    1000
Gid:    1000    1000    1000    1000
FDSize: 256
Groups: 4 20 24 27 30 46 107 123 124 1000 
VmPeak:     4300 kB
VmSize:     4300 kB
VmLck:         0 kB
VmPin:         0 kB
VmHWM:       356 kB
VmRSS:       356 kB
VmData:      188 kB
VmStk:       136 kB
VmExe:         4 kB
VmLib:      1884 kB
VmPTE:        32 kB
VmSwap:        0 kB
Threads:        1
SigQ:   0/22869
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000000000000
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: ffffffffffffffff
Cpus_allowed:   3
Cpus_allowed_list:      0-1
Mems_allowed:   00000000,00000001
Mems_allowed_list:      0
voluntary_ctxt_switches:        1
nonvoluntary_ctxt_switches:     1
Terminating func...

So in a word, what does my program do? He creates a new thread with cloneand prints it /proc/self/statusso that I can see its status. Since my thread sleeps for 1 second, it is still alive when printed /proc/self/status.

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