From 014b45b4a98354291cfc7ede8f90d2da4ca5ff2f Mon Sep 17 00:00:00 2001
From: "David R. MacIver" <david@drmaciver.com>
Date: Tue, 10 Dec 2013 09:17:30 +0000
Subject: [PATCH 1/2] add checking of numeric indices to an array to see if
 they can reasonably be considered integers. Avoid undefined behaviour if out
 of bounds

---
 jv.c           | 12 ++++++++++++
 jv.h           |  1 +
 jv_aux.c       | 13 +++++++++----
 tests/all.test |  4 ++++
 4 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/jv.c b/jv.c
index eea6a290..d1ae8d90 100644
--- a/jv.c
+++ b/jv.c
@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdarg.h>
+#include <limits.h>
 
 #include "jv_alloc.h"
 #include "jv.h"
@@ -140,6 +141,17 @@ double jv_number_value(jv j) {
   return j.u.number;
 }
 
+int jv_is_integer(jv j){
+  if(jv_get_kind(j) != JV_KIND_NUMBER){
+    return 0;
+  }
+  double x = jv_number_value(j);
+  if(x != x || x > INT_MAX || x < INT_MIN){
+    return 0;
+  }
+
+  return x == (int)x;
+}
 
 /*
  * Arrays (internal helpers)
diff --git a/jv.h b/jv.h
index 8d61d104..70024735 100644
--- a/jv.h
+++ b/jv.h
@@ -60,6 +60,7 @@ jv jv_bool(int);
 
 jv jv_number(double);
 double jv_number_value(jv);
+int jv_is_integer(jv);
 
 jv jv_array();
 jv jv_array_sized(int);
diff --git a/jv_aux.c b/jv_aux.c
index 76712aee..e994053d 100644
--- a/jv_aux.c
+++ b/jv_aux.c
@@ -51,10 +51,15 @@ jv jv_get(jv t, jv k) {
       v = jv_null();
     }
   } else if (jv_get_kind(t) == JV_KIND_ARRAY && jv_get_kind(k) == JV_KIND_NUMBER) {
-    // FIXME: don't do lookup for noninteger index
-    v = jv_array_get(t, (int)jv_number_value(k));
-    if (!jv_is_valid(v)) {
-      jv_free(v);
+    if(jv_is_integer(k)){
+      v = jv_array_get(t, (int)jv_number_value(k));
+      if (!jv_is_valid(v)) {
+        jv_free(v);
+        v = jv_null();
+      }
+    } else {
+      jv_free(t);
+      jv_free(k);
       v = jv_null();
     }
   } else if (jv_get_kind(t) == JV_KIND_ARRAY && jv_get_kind(k) == JV_KIND_OBJECT) {
diff --git a/tests/all.test b/tests/all.test
index 71918a6f..15e075d4 100644
--- a/tests/all.test
+++ b/tests/all.test
@@ -718,3 +718,7 @@ map(has(2))
 keys
 [42,3,35]
 [0,1,2]
+
+[][.]
+1000000000000000000
+null

From 5412f3f1c1cade37041c2770ab328c146cf7c74a Mon Sep 17 00:00:00 2001
From: "David R. MacIver" <david@drmaciver.com>
Date: Tue, 10 Dec 2013 09:18:16 +0000
Subject: [PATCH 2/2] convert range bounds to integers in a way that avoids
 undefined behaviour

---
 jv_aux.c       | 17 +++++++++++------
 tests/all.test |  4 ++++
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/jv_aux.c b/jv_aux.c
index e994053d..ec2aaa18 100644
--- a/jv_aux.c
+++ b/jv_aux.c
@@ -26,13 +26,18 @@ static int parse_slice(jv j, jv slice, int* pstart, int* pend) {
     jv_free(end_jv);
     return 0;
   } else {
-    int start = (int)jv_number_value(start_jv);
-    int end = (int)jv_number_value(end_jv);
-    if (start < 0) start = len + start;
-    if (end < 0) end = len + end;
+    double dstart = jv_number_value(start_jv);
+    double dend = jv_number_value(end_jv);
+    if (dstart < 0) dstart += len;
+    if (dend < 0) dend += len;
+    if (dstart < 0) dstart = 0;
+    if (dstart > len) dstart = len;
+
+    int start = (int)dstart;
+    int end = (dend > len) ? len : (int)dend;
+    // Ends are exclusive but e.g. 1 < 1.5 so :1.5 should be :2 not :1
+    if(end < dend) end += 1;
 
-    if (start < 0) start = 0;
-    if (start > len) start = len;
     if (end > len) end = len;
     if (end < start) end = start;
     assert(0 <= start && start <= end && end <= len);
diff --git a/tests/all.test b/tests/all.test
index 15e075d4..3615bee9 100644
--- a/tests/all.test
+++ b/tests/all.test
@@ -722,3 +722,7 @@ keys
 [][.]
 1000000000000000000
 null
+
+map([1,2][0:.])
+[-1, 1, 2, 3, 1000000000000000000]
+[[1], [1], [1,2], [1,2], [1,2]]