[CF 5882] GNU/Hurd portability patches

This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/5882

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/[email protected]
Author(s): Michael Banck

Author: Commitfest Bot

src/backend/storage/file/fd.c

@@ -411,14 +411,12 @@ pg_fsync(int fd)
 	{
 		int			desc_flags = fcntl(fd, F_GETFL);
 
-		/*
-		 * O_RDONLY is historically 0, so just make sure that for directories
-		 * no write flags are used.
-		 */
+		desc_flags &= O_ACCMODE;
+
 		if (S_ISDIR(st.st_mode))
-			Assert((desc_flags & (O_RDWR | O_WRONLY)) == 0);
+			Assert(desc_flags == O_RDONLY);
 		else
-			Assert((desc_flags & (O_RDWR | O_WRONLY)) != 0);
+			Assert(desc_flags != O_RDONLY);
 	}
 	errno = 0;
 #endif

src/include/port/pg_iovec.h

@@ -21,9 +21,6 @@
 
 #else
 
-/* POSIX requires at least 16 as a maximum iovcnt. */
-#define IOV_MAX 16
-
 /* Define our own POSIX-compatible iovec struct. */
 struct iovec
 {
@@ -33,6 +30,11 @@ struct iovec
 
 #endif
 
+/* POSIX requires at least 16 as a maximum iovcnt. */
+#ifndef IOV_MAX
+#define IOV_MAX 16
+#endif
+
 /*
  * Define a reasonable maximum that is safe to use on the stack in arrays of
  * struct iovec and other small types.  The operating system could limit us to