Improve documentation of hash-code functions

* src/fns.c (Fsxhash_eq, Fsxhash_eql, Fsxhash_equal):
* doc/lispref/hash.texi (Defining Hash): Warn against assuming
that sxhash returns consistent results.

1 files changed, 5 insertions, 0 deletions

diff --git a/doc/lispref/hash.texi b/doc/lispref/hash.texi
index 5aaf31247b4..9b900e63099 100644
--- a/doc/lispref/hash.texi
+++ b/doc/lispref/hash.texi
@@ -333,6 +333,11 @@ and equal-looking objects are considered the same key.
 (make-hash-table :test 'contents-hash)
 @end example
 
+Lisp programs should @emph{not} rely on hash codes being preserved
+between Emacs sessions, as the implementation of the hash functions
+uses some details of the object storage that can change between
+sessions and between different architectures.
+
 @node Other Hash
 @section Other Hash Table Functions