poll: Fixed a malfunction with wrong max fd value check.

include/libssh/libssh.h

@@ -120,10 +120,14 @@ typedef struct ssh_string_struct* ssh_string;
 
 /* Socket type */
 #ifdef _WIN32
-#define socket_t SOCKET
-#else
+#ifndef socket_t
+typedef SOCKET socket_t;
+#endif /* socket_t */
+#else /* _WIN32 */
+#ifndef socket_t
 typedef int socket_t;
 #endif
+#endif /* _WIN32 */
 
 /* the offsets of methods */
 enum ssh_kex_types_e {

libssh/poll.c

@@ -135,7 +135,7 @@ static int bsd_poll(ssh_pollfd_t *fds, nfds_t nfds, int timeout) {
   FD_ZERO (&exceptfds);
 
   /* compute fd_sets and find largest descriptor */
-  for (max_fd = -1, i = 0; i < nfds; i++) {
+  for (max_fd = 0, i = 0; i < nfds; i++) {
       if (fds[i].fd < 0) {
           continue;
       }
@@ -157,7 +157,7 @@ static int bsd_poll(ssh_pollfd_t *fds, nfds_t nfds, int timeout) {
       }
   }
 
-  if (max_fd == -1) {
+  if (max_fd == (socket_t) -1) {
       errno = EINVAL;
       return -1;
   }