Subject: incomplete type 'struct pollfd', etc., when compiling tail on MacOS (patch included)
From: Dennis Williamson <[email-masked]>
To: [email-masked]
Date: Sun, 4 Dec 2022 09:55:03 -0600
List-Id: <debbugs-submit.debbugs.gnu.org>

I received the errors for tail.c shown below when compiling coreutils on 
MacOS (11.6). Adding __APPLE__ to the #if defined for poll.h fixes the 
issue (see the diff at the bottom). Making this change matches that line 
to the one within check_output_alive().

commit 324c188cfd8a1628c260e5003d309613a0c66e57 (August 29, 2022) made 
the change to check_output_alive(), but missed the change reported here.

Dennis

(HEAD: aaa306ad76d48b27efd75101d57b6ec5bf90362c)

Error:

   CC       src/tail.o
src/tail.c:367:17: error: variable has incomplete type 'struct pollfd'
   struct pollfd pfd;
                 ^
src/tail.c:367:10: note: forward declaration of 'struct pollfd'
   struct pollfd pfd;
          ^
src/tail.c:370:17: error: use of undeclared identifier 'POLLRDBAND'
   pfd.events |= POLLRDBAND; /* Needed for illumos, macos.  */
                 ^
src/tail.c:372:7: error: implicit declaration of function 'poll' is 
invalid in C99 [-Werror,-Wimplicit-function-declaration]
   if (poll (&pfd, 1, 0) >= 0 && (pfd.revents & (POLLERR | POLLHUP)))
       ^
src/tail.c:372:49: error: use of undeclared identifier 'POLLERR'
   if (poll (&pfd, 1, 0) >= 0 && (pfd.revents & (POLLERR | POLLHUP)))
                                                 ^
src/tail.c:372:59: error: use of undeclared identifier 'POLLHUP'
   if (poll (&pfd, 1, 0) >= 0 && (pfd.revents & (POLLERR | POLLHUP)))
                                                           ^
5 errors generated.
make[2]: *** [src/tail.o] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2

Diff:

diff --git a/src/tail.c b/src/tail.c
index 6c7d59faf..14abf0871 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -55,7 +55,7 @@
  # include <sys/inotify.h>
  #endif

-#if defined _AIX || defined __sun || HAVE_INOTIFY
+#if defined _AIX || defined __sun || defined __APPLE__ || HAVE_INOTIFY
  # include <poll.h>
  #endif