From 6f10f06c2776c8dfa7e727f2a000dc48bd296bf0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Lindqvist?= <bjourne@gmail.com>
Date: Wed, 5 Oct 2016 19:09:55 +0200
Subject: [PATCH] hash-sets,hashtables: make it so the array backing the hash
 is non-empty

Commit 70c7f9e02910746918cc16bf588ef543fda80790 made it so the code
assumes the array is not empty. But it can be empty if the hashtable is
created using "hashtable new" and then it can crash because it reads
uninitialized memory. Setting the initial of the array slot to
a valid hash-array should fix that.
---
 core/hash-sets/hash-sets.factor         |  5 ++++-
 core/hashtables/hashtables-tests.factor | 21 ++++++++++++++++++---
 core/hashtables/hashtables.factor       |  8 +++++++-
 3 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/core/hash-sets/hash-sets.factor b/core/hash-sets/hash-sets.factor
index 03577db12a..6bbd327371 100644
--- a/core/hash-sets/hash-sets.factor
+++ b/core/hash-sets/hash-sets.factor
@@ -10,7 +10,10 @@ IN: hash-sets
 TUPLE: hash-set
     { count array-capacity }
     { deleted array-capacity }
-    { array array } ;
+    { array array initial: {
+          T{ tombstone } T{ tombstone } T{ tombstone } T{ tombstone }
+      }
+    } ;
 
 <PRIVATE
 
diff --git a/core/hashtables/hashtables-tests.factor b/core/hashtables/hashtables-tests.factor
index a238eef90d..1ae6ad353c 100644
--- a/core/hashtables/hashtables-tests.factor
+++ b/core/hashtables/hashtables-tests.factor
@@ -1,5 +1,11 @@
-USING: accessors assocs continuations fry hashtables kernel make
-math namespaces sequences tools.test ;
+USING: accessors arrays assocs continuations fry hashtables
+hashtables.private kernel make math memory namespaces sequences
+tools.test ;
+
+! hash@
+{ 18 } [
+    77 20 f <array> hash@
+] unit-test
 
 { H{ } } [ { } [ dup ] H{ } map>assoc ] unit-test
 
@@ -182,5 +188,14 @@ H{ } "x" set
 
 { 1 } [ 2 "h" get at ] unit-test
 
+! Previously this could break as hashtable new created a backing an
+! empty backing array and the code assumed its length was > 0.
+{ f f } [
+    compact-gc 77 hashtable new [ clone ] change-array at*
+] unit-test
+
 ! Random test case
-{ "A" } [ 100 iota [ dup ] H{ } map>assoc 32 over delete-at "A" 32 pick set-at 32 of ] unit-test
+{ "A" } [
+    100 iota [ dup ] H{ } map>assoc 32 over
+    delete-at "A" 32 pick set-at 32 of
+] unit-test
diff --git a/core/hashtables/hashtables.factor b/core/hashtables/hashtables.factor
index ee14103cb8..6e2903d8ee 100644
--- a/core/hashtables/hashtables.factor
+++ b/core/hashtables/hashtables.factor
@@ -4,10 +4,16 @@ USING: accessors arrays assocs kernel kernel.private math
 math.private sequences sequences.private slots.private vectors ;
 IN: hashtables
 
+! Required because the hashtable definition references tombstone.
+<PRIVATE PRIVATE>
+
 TUPLE: hashtable
     { count array-capacity }
     { deleted array-capacity }
-    { array array } ;
+    { array array initial: {
+          T{ tombstone } T{ tombstone } T{ tombstone } T{ tombstone }
+      }
+    } ;
 
 <PRIVATE