poll: enable argument check

[Bruno Haible]

On Mac OS X, I'm seeing this warning:


poll.c:338:11: warning: comparison of unsigned expression < 0 is always false 
[-Wtautological-compare]
  if (nfd < 0)
      ~~~ ^ ~

Indeed, nfd is of type nfds_t, which is an unsigned integer type per POSIX [1].

This fixes it:

2017-04-22  Bruno Haible  <address@hidden>

        poll: Enable argument check.
        * lib/poll.c: Include intprops.h.
        (poll): Check value of nfd correctly.
        * modules/poll (Depends-on): Add intprops.

diff --git a/lib/poll.c b/lib/poll.c
index 88d9292..803ac0e 100644
--- a/lib/poll.c
+++ b/lib/poll.c
@@ -60,6 +60,7 @@
 #include <time.h>
 
 #include "assure.h"
+#include "intprops.h"
 
 #ifndef INFTIM
 # define INFTIM (-1)
@@ -335,7 +336,7 @@ poll (struct pollfd *pfd, nfds_t nfd, int timeout)
   int maxfd, rc;
   nfds_t i;
 
-  if (nfd < 0)
+  if (nfd > TYPE_MAXIMUM (nfds_t) / 2)
     {
       errno = EINVAL;
       return -1;
diff --git a/modules/poll b/modules/poll
index 57f0631..a7d117f 100644
--- a/modules/poll
+++ b/modules/poll
@@ -9,6 +9,7 @@ Depends-on:
 poll-h
 alloca          [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]
 assure          [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]
+intprops        [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]
 select          [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]
 sockets         [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]
 sys_select      [test $HAVE_POLL = 0 || test $REPLACE_POLL = 1]



[1] http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/poll.h.html