find: fix visiting of files with inode number Zero

On GNU/Hurd, the value 0 is a valid inode number, and is e.g. used
for /dev/console and /dev/tty.  The find(1) program aborted on this
platform when the user specified the -inum test and when the search
visited such a file.

  $ find /dev/null /dev/tty -inum 40799 -printf '%i:%p\n'
  40799:/dev/null
  find: util.c:330: get_info: Assertion `p->st_ino' failed.
  Aborted

Likewise, 'find -printf %i' aborted when hitting such a file.

* find/defs.h (get_info): Remove declaration.
* find/pred.c (pred_inum): Remove the redundant assert for ST_INO
as parse_inum sets need_inum=true which ensures that the inode number
is known.
* find/util.c (get_info): Declare static, and simplify: remove the
assertions for the inode number and file type.
While at it, add condition !state.have_stat in the need_stat case
for consistency.
* tests/find/inode-zero.sh: Add test.
* tests/local.mk (all_tests): Reference it.

Problem introduced by the inum optimisation in commit 2bf001636e6.

Reported by Andrea Monaco <andrea.monaco@autistici.org> in
https://lists.gnu.org/r/bug-findutils/2021-12/msg00008.html

1 files changed, 5 insertions, 26 deletions

diff --git a/find/util.c b/find/util.c
index afd9880e..59f80659 100644
--- a/find/util.c
+++ b/find/util.c
@@ -280,7 +280,7 @@ get_statinfo (const char *pathname, const char *name, struct stat *p)
 /* Get the stat/type/inode information for a file, if it is not
  * already known.   Returns 0 on success (or if we did nothing).
  */
-int
+static int
 get_info (const char *pathname,
 	  struct stat *p,
 	  struct predicate *pred_ptr)
@@ -290,7 +290,7 @@ get_info (const char *pathname,
   /* If we need the full stat info, or we need the type info but don't
    * already have it, stat the file now.
    */
-  if (pred_ptr->need_stat)
+  if (pred_ptr->need_stat && !state.have_stat)
     {
       todo = true;		/* need full stat info */
     }
@@ -316,31 +316,10 @@ get_info (const char *pathname,
     }
   if (todo)
     {
-      int result = get_statinfo (pathname, state.rel_pathname, p);
-      if (result != 0)
-	{
-	  return -1;		/* failure. */
-	}
-      else
-	{
-	  /* Verify some postconditions.  We can't check st_mode for
-	     non-zero-ness because of Savannah bug #16378 (which is
-	     that broken NFS servers can return st_mode==0). */
-	  if (pred_ptr->need_type)
-	    {
-	      assert (state.have_type);
-	    }
-	  if (pred_ptr->need_inum)
-	    {
-	      assert (p->st_ino);
-	    }
-	  return 0;		/* success. */
-	}
-    }
-  else
-    {
-      return 0;			/* success; nothing to do. */
+      if (get_statinfo (pathname, state.rel_pathname, p) != 0)
+	return -1;		/* failure. */
     }
+  return 0;			/* success, or nothing to do. */
 }
 
 /* Determine if we can use O_NOFOLLOW.