Parallelizing with openmp makes memory leak - c++

Question

#include <iostream>
#include <random>
int main()
{
int a;
int *arr;
a = 3;
arr = new int[a];
#pragma omp parallel for
for (int i = 0; i < a; i++)
arr[i] = i;
delete[] arr;
return 0;
}
When I test this simple code with valgrind, it saids:
==2606== HEAP SUMMARY:
==2606== in use at exit: 3,360 bytes in 7 blocks
==2606== total heap usage: 10 allocs, 3 frees, 108,892 bytes allocated
==2606==
==2606== LEAK SUMMARY:
==2606== definitely lost: 0 bytes in 0 blocks
==2606== indirectly lost: 0 bytes in 0 blocks
==2606== possibly lost: 912 bytes in 3 blocks
==2606== still reachable: 2,448 bytes in 4 blocks
==2606== suppressed: 0 bytes in 0 blocks
Am I misunderstanding openmp or memory allocation usage?
Without "#pragma omp parallel for", it doesn't make any issues.
UPDATE
==2682== 912 bytes in 3 blocks are possibly lost in loss record 4 of 5
==2682== at 0x483DD99: calloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==2682== by 0x40149DA: allocate_dtv (dl-tls.c:286)
==2682== by 0x40149DA: _dl_allocate_tls (dl-tls.c:532)
==2682== by 0x4DE4322: allocate_stack (allocatestack.c:622)
==2682== by 0x4DE4322: pthread_create##GLIBC_2.2.5 (pthread_create.c:660)
==2682== by 0x4A4FDEA: ??? (in /usr/lib/x86_64-linux-gnu/libgomp.so.1.0.0)
==2682== by 0x4A478E0: GOMP_parallel (in /usr/lib/x86_64-linux-gnu/libgomp.so.1.0.0)
==2682== by 0x109184: main (main.cpp:10)
This is what --leak-check-full says.