problem s funkci res_query v RH8

[Leo Hadacz]

Zdravim,

mam nasledujici kratky kod:

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#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <resolv.h>                     // defines for name server and IPv6
#include <arpa/nameser.h>               // nameserver definitions
#include <pthread.h>

int make_res();
void * thr1_func (void *);

int main (int argc, char *argv[])
{
    pthread_t thr1;
    printf ("Outside any thread.\n");
    make_res();
    pthread_create (&thr1, NULL, thr1_func, NULL);
    pthread_join (thr1, NULL);
    printf ("The threads are finished.\n");
    exit (EXIT_SUCCESS);
}

int make_res()
{
  char *domain = "uuu.xxx";
  char srv[MAXDNAME];
  unsigned char response[4096];  // response header+buffer
  int len;                       // buffer length
  sprintf(srv, "%s.%s.%s.", "aaa", "bbb", domain);
  if ((len = res_query (srv, C_IN, T_SRV, response, sizeof (response))) > 0) {
    printf ("res_query: DNS search OK.\n");
    return 0;
  }
  else {
    printf ("res_query: DNS search failed!\n");
    return -1;
  }
}

void * thr1_func (void *nothing)
{

    printf ("I am thread 1.\n");
    sleep(1);
    make_res();
    return (NULL);
}
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ktery prekladam takto:
g++ -c -Wall -D_REENTRANT -DLINUX -DUSE_SBUF dp-thr1.cpp -o dp-thr1.o
g++  dp-thr1.o -lpthread -lresolv -o dp-thr1

Odpovidajici zaznam v DNS je
aaa.bbb   IN SRV  0   1   3306    some_value

Na RedHatu 7.3 funguji obe volani funkce res_query: mimo thread i uvnitr
threadu. Tedy vysledek spusteni je:
---------------------------
$ ./dp-thr1
Outside any thread.
res_query: DNS search OK.
I am thread 1.
res_query: DNS search OK.
The threads are finished.
---------------------------

Na RedHatu 8.0 volani res_query mimo thread dopadne dobre, ale uvnitr
threadu skonci s chybou (funkce vrati -1), tj. vysledek je:
$ ./dp-thr1
Outside any thread.
res_query: DNS search OK.
I am thread 1.
res_query: DNS search failed!
The threads are finished.
---------------------------

Nevite nekdo co je spatne? 

Leo

-- 
Leo Hadacz, ANF DATA / Siemens, +420 54310 6586