Use poll's data types directly, where used at all

[smcv: added commit message; moved fallback implementation
below definition of DBusPollable; more comments; removed unnecessary cast]
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=90314Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>

dbus/dbus-sysdeps-unix.c

@@ -2752,43 +2752,17 @@ _dbus_poll (DBusPollFD *fds,
             int         timeout_milliseconds)
 {
 #if defined(HAVE_POLL) && !defined(BROKEN_POLL)
-  /* This big thing is a constant expression and should get optimized
-   * out of existence. So it's more robust than a configure check at
-   * no cost.
-   */
-  if (_DBUS_POLLIN == POLLIN &&
-      _DBUS_POLLPRI == POLLPRI &&
-      _DBUS_POLLOUT == POLLOUT &&
-      _DBUS_POLLERR == POLLERR &&
-      _DBUS_POLLHUP == POLLHUP &&
-      _DBUS_POLLNVAL == POLLNVAL &&
-      sizeof (DBusPollFD) == sizeof (struct pollfd) &&
-      _DBUS_STRUCT_OFFSET (DBusPollFD, fd) ==
-      _DBUS_STRUCT_OFFSET (struct pollfd, fd) &&
-      _DBUS_STRUCT_OFFSET (DBusPollFD, events) ==
-      _DBUS_STRUCT_OFFSET (struct pollfd, events) &&
-      _DBUS_STRUCT_OFFSET (DBusPollFD, revents) ==
-      _DBUS_STRUCT_OFFSET (struct pollfd, revents))
+  /* DBusPollFD is a struct pollfd in this code path, so we can just poll() */
+  if (timeout_milliseconds < -1)
     {
-      if (timeout_milliseconds < -1)
-        {
-          timeout_milliseconds = -1;
-        }
-
-      return poll ((struct pollfd*) fds,
-                   n_fds,
-                   timeout_milliseconds);
+      timeout_milliseconds = -1;
     }
-  else
-    {
-      /* We have to convert the DBusPollFD to an array of
-       * struct pollfd, poll, and convert back.
-       */
-      _dbus_warn ("didn't implement poll() properly for this system yet\n");
-      return -1;
-    }
-#else /* ! HAVE_POLL */
 
+  return poll (fds,
+               n_fds,
+               timeout_milliseconds);
+#else /* ! HAVE_POLL */
+  /* Emulate poll() in terms of select() */
   fd_set read_set, write_set, err_set;
   int max_fd = 0;
   int i;

dbus/dbus-sysdeps.h

@@ -299,63 +299,6 @@ dbus_int32_t _dbus_atomic_inc (DBusAtomic *atomic);
 dbus_int32_t _dbus_atomic_dec (DBusAtomic *atomic);
 dbus_int32_t _dbus_atomic_get (DBusAtomic *atomic);
 
-
-/* AIX uses different values for poll */
-
-#ifdef _AIX
-/** There is data to read */
-#define _DBUS_POLLIN      0x0001
-/** There is urgent data to read */
-#define _DBUS_POLLPRI     0x0004
-/** Writing now will not block */
-#define _DBUS_POLLOUT     0x0002
-/** Error condition */
-#define _DBUS_POLLERR     0x4000
-/** Hung up */
-#define _DBUS_POLLHUP     0x2000
-/** Invalid request: fd not open */
-#define _DBUS_POLLNVAL    0x8000
-#elif defined(__HAIKU__)
-/** There is data to read */
-#define _DBUS_POLLIN      0x0001
-/** Writing now will not block */
-#define _DBUS_POLLOUT     0x0002
-/** Error condition */
-#define _DBUS_POLLERR     0x0004
-/** There is urgent data to read */
-#define _DBUS_POLLPRI     0x0020
-/** Hung up */
-#define _DBUS_POLLHUP     0x0080
-/** Invalid request: fd not open */
-#define _DBUS_POLLNVAL    0x1000
-#elif defined(__QNX__)
-/** Writing now will not block */
-#define _DBUS_POLLOUT     0x0002
-/** There is data to read */
-#define _DBUS_POLLIN      0x0005
-/** There is urgent data to read */
-#define _DBUS_POLLPRI     0x0008
-/** Error condition */
-#define _DBUS_POLLERR     0x0020
-/** Hung up */
-#define _DBUS_POLLHUP     0x0040
-/** Invalid request: fd not open */
-#define _DBUS_POLLNVAL    0x1000
-#else
-/** There is data to read */
-#define _DBUS_POLLIN      0x0001
-/** There is urgent data to read */
-#define _DBUS_POLLPRI     0x0002
-/** Writing now will not block */
-#define _DBUS_POLLOUT     0x0004
-/** Error condition */
-#define _DBUS_POLLERR     0x0008
-/** Hung up */
-#define _DBUS_POLLHUP     0x0010
-/** Invalid request: fd not open */
-#define _DBUS_POLLNVAL    0x0020
-#endif
-
 #ifdef DBUS_WIN
 
 /* On Windows, you can only poll sockets. We emulate Unix poll() using
@@ -407,9 +350,30 @@ _dbus_pollable_equals (DBusPollable a, DBusPollable b) { return a == b; }
 
 #endif /* !DBUS_WIN */
 
+#if defined(HAVE_POLL) && !defined(BROKEN_POLL)
 /**
- * A portable struct pollfd wrapper. 
+ * A portable struct pollfd wrapper, or an emulation of struct pollfd
+ * on platforms where poll() is missing or broken.
  */
+typedef struct pollfd DBusPollFD;
+
+/** There is data to read */
+#define _DBUS_POLLIN      POLLIN
+/** There is urgent data to read */
+#define _DBUS_POLLPRI     POLLPRI
+/** Writing now will not block */
+#define _DBUS_POLLOUT     POLLOUT
+/** Error condition */
+#define _DBUS_POLLERR     POLLERR
+/** Hung up */
+#define _DBUS_POLLHUP     POLLHUP
+/** Invalid request: fd not open */
+#define _DBUS_POLLNVAL    POLLNVAL
+#else
+/* Emulate poll() via select(). Because we aren't really going to call
+ * poll(), any similarly-shaped struct is acceptable, and any power of 2
+ * will do for the events/revents; these values happen to match Linux
+ * and *BSD. */
 typedef struct
 {
   DBusPollable fd;   /**< File descriptor */
@@ -417,6 +381,20 @@ typedef struct
   short revents;     /**< Events that occurred */
 } DBusPollFD;
 
+/** There is data to read */
+#define _DBUS_POLLIN      0x0001
+/** There is urgent data to read */
+#define _DBUS_POLLPRI     0x0002
+/** Writing now will not block */
+#define _DBUS_POLLOUT     0x0004
+/** Error condition */
+#define _DBUS_POLLERR     0x0008
+/** Hung up */
+#define _DBUS_POLLHUP     0x0010
+/** Invalid request: fd not open */
+#define _DBUS_POLLNVAL    0x0020
+#endif
+
 DBUS_PRIVATE_EXPORT
 int _dbus_poll (DBusPollFD *fds,
                 int         n_fds,