[Valgrind-users] Error when analysing pthreads code?

[EML <sa2...@cy...>]

The program below creates two threads, in a detached state, and waits 
for them to complete with 'pthread_exit'. Compile and run as:

 > gcc -lpthread test.c
 > valgrind --leak-check=full a.out

valgrind-3.13.0 (compiled from source) reports no errors on some runs, 
and a possible leak on other runs (560 bytes in 1 blocks), fairly 
randomly. On my system, the ratio of error-free to bad runs is about 50/50.

Is this is a problem with valgrind, or my use of pthreads? *Note that 
this isn't the standard 'pthread_create' memory leak with joinable 
threads which haven't been joined, since the threads are detached.* I'm 
compiling on Centos 6.9, gcc 4.4.7. Thanks.

------------------------------------------------------------------------
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>

void *thread(void *data) {
    printf("in new thread %ld\n", (long)data);
}

int main() {
    pthread_t      thread_id[2];
    pthread_attr_t thread_attr;
    int failed = 1;

    do {
       if(pthread_attr_init(&thread_attr))
          break;
       if(pthread_attr_setdetachstate(&thread_attr, 
PTHREAD_CREATE_DETACHED))
          break;
       if(pthread_create(&thread_id[0], &thread_attr, thread, (void*)0))
          break;
       if(pthread_create(&thread_id[1], &thread_attr, thread, (void*)1))
          break;
       failed = 0;
    } while(0);

    if(failed) {
       printf("pthreads call failed\n");
       exit(1);
    }

    pthread_exit(0);
}
------------------------------------------------------------------------