readdir_r hangs

/* file foo.c
 *
 * Desc: Seems that readdir_r from glibc is blocking ..
 * Compile: gcc -g -o foo foo.c
 * Run:
 *   create two directories one inside another
 *   # mkdir -p bar/tar
 *   now run as
 *   # ./foo bar tar
 *
 */
#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define pexit(msg)                              \
        do {                                    \
                perror(msg);                    \
                exit(EXIT_FAILURE);             \
        } while (0)




int main(int argc, char **argv)
{
        struct dirent *dirp;
        static struct dirent dirbuff;
        struct dirent *result = NULL;

        dirp = (struct dirent *) opendir(argv[1]);
        if (!dirp)
                pexit("opendir");

        while (1) {
                int error = readdir_r((DIR *)dirp, &dirbuff, &result);
                if (error)
                        pexit("readdir_r");

                if (!result)
                        break;

                printf("at %s\n", dirp->d_name);
                printf("read %s\n", dirbuff.d_name);

                if (strcmp(dirbuff.d_name, argv[2]) == 0) {
                        printf("entering in %s\n", argv[2]);
                        result == NULL;
                        dirp = &dirbuff;
                        continue;
                }
        }
        return 0;
}