C pthread_create causing memory leak - c

Question

I have a multi-threaded application which uses joinable threads.
In order to create the threads (which are in total nthreads workers+1 additional thread) I use a regular call to pthread_create.
However, when I try to debug memory leaks, I get a x bytes in y blocks are possibly lost in loss record z of w error, caused by the pthread_create calls.
Here is the part of the code of the program relevant to the issue :
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <errno.h>
int main(){
int i=0;
int nthreads=8;
pthread_t tid_w[nthreads+1];
if( pthread_create(&tid_w[0], NULL, dispatcher, (void*) (size_t) i)<0){
perror("Creating dispatcher thread");
return -1;
}
for(i=1; i<nthreads+1; i++){
if( pthread_create(&tid_w[i], NULL, worker, (void*) (size_t) i)<0){
perror("Creating worker thread");
return -1;
}
}
// thread joining
for(i=0; i<nthreads+1; i++){
if( pthread_join(tid_w[i], NULL)<0){
perror("Joining thread");
return -1;
}
}
return 0;
}
This is the output of valgrind (3.11)
==14418==
==14418== HEAP SUMMARY:
==14418== in use at exit: 14,496 bytes in 21 blocks
==14418== total heap usage: 25 allocs, 4 frees, 15,724 bytes allocated
==14418==
==14418== 560 bytes in 1 blocks are possibly lost in loss record 12 of 14
==14418== at 0x4C2DB95: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==14418== by 0x40134C4: allocate_dtv (dl-tls.c:322)
==14418== by 0x40134C4: _dl_allocate_tls (dl-tls.c:544)
==14418== by 0x4E400D2: allocate_stack (allocatestack.c:588)
==14418== by 0x4E400D2: pthread_create##GLIBC_2.2.5 (pthread_create.c:537)
==14418== by 0x4018AE: main (chatty.c:132)
==14418==
==14418== 4,480 bytes in 8 blocks are possibly lost in loss record 13 of 14
==14418== at 0x4C2DB95: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==14418== by 0x40134C4: allocate_dtv (dl-tls.c:322)
==14418== by 0x40134C4: _dl_allocate_tls (dl-tls.c:544)
==14418== by 0x4E400D2: allocate_stack (allocatestack.c:588)
==14418== by 0x4E400D2: pthread_create##GLIBC_2.2.5 (pthread_create.c:537)
==14418== by 0x401909: main (chatty.c:138)
==14418==
==14418== LEAK SUMMARY:
==14418== definitely lost: 0 bytes in 0 blocks
==14418== indirectly lost: 0 bytes in 0 blocks
==14418== possibly lost: 5,040 bytes in 9 blocks
==14418== still reachable: 9,456 bytes in 12 blocks
==14418== suppressed: 0 bytes in 0 blocks
==14418== Reachable blocks (those to which a pointer was found) are not shown.
==14418== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==14418==
==14418== For counts of detected and suppressed errors, rerun with: -v
==14418== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)
Line numbers might not match because I have removed a few socket-related parts from the code.
I also have read a lot about pthread_create causing memory leaks but it seems like the issue presents itself when in use of detached threads, which is not my case.
Any idea on how to solve the issue?