Fix cpnet_getHostByName return value on error

In platforms lacking gethostbyname_r, such as Darwin (macOS),
cpnet_getHostByName incorrectly returns -errno when gethostbyname
fails. It should return -h_errno instead.

Since errno is not set by gethostbyname, the value returned by
cpnet_getHostByName is undefined at that point. It could be 0 or
a stale value from a previous unrelated system call.

If cpnet_getHostByName returns 0 (CPNATIVE_OK) the caller
(Java_java_net_VMInetAddress_getHostByName) then proceeds to
access the addresses pointer, which was never initialized,
typically leading to a crash (SIGBUS/SIGSEGV).

Fix by returning -h_errno on error.

Fixes #37 (BZ#124082)

Signed-off-by: Guillermo Rodríguez <grodriguez@ingelabs.com>

Author: guillerodriguez

native/jni/native-lib/cpnet.c

@@ -661,7 +661,7 @@ jint cpnet_getHostByName (JNIEnv *env, const char *hostname, cpnet_address ***ad
 
       result = gethostbyname (hostname);
       if (result == NULL)
-        return -errno;
+        return -h_errno;
       memcpy (&hret, result, sizeof (struct hostent));
 #endif
       if (ret != 0 || result == NULL)