#include <pwd.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

int main(void) {
  struct passwd pwd;
  struct passwd *pwdres;
  char buf[10000];
  int res = getpwnam_r("no-such-user", &pwd, buf, sizeof(buf), &pwdres);
  printf("res: %d\n", res);
  printf("(pwdres == 0): %d\n", (int)(pwdres == 0));
  return 0;
}


According to the getpwnam_r documentation 

On success, getpwnam_r() and getpwuid_r() return zero, and set *result to pwd. If no matching password record was found, these functions return 0 and store NULL in *result. In case of error, an error number is returned, and NULL is stored in *result. 

this program should print

res: 0
(pwdres == 0): 1

but on some power systems "res" is non-zero (specifically 2).  I tried it on several power systems and on some it worked properly and others not (both BE and LE).  I also tried it on an x86 system and it worked properly there.

It failed on systems with version 2.17 and 2.20 but worked on ones with 2.15 and 2.19 so I am not sure what releases are really affected.