libmdb: Fix P_INVALID when pgno_t != unsigned long

diff --git a/libraries/libmdb/mdb.c b/libraries/libmdb/mdb.c
index e3ad1c4..6be2103 100644 (file)
--- a/libraries/libmdb/mdb.c
+++ b/libraries/libmdb/mdb.c
@@ -342,7 +342,7 @@ static txnid_t mdb_debug_start;
        /** An invalid page number.
         *      Mainly used to denote an empty tree.
         */
-#define P_INVALID       (~0UL)
+#define P_INVALID       (~(pgno_t)0)
 
        /** Test if a flag \b f is set in a flag word \b w. */
 #define F_ISSET(w, f)   (((w) & (f)) == (f))