From 3c878b1e3bbb043b22ab032bce1fe111b8062ca9 Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@wolfbeast.com>
Date: Mon, 17 Jun 2019 18:37:23 +0000
Subject: Convert CopyBoxedOrUnboxedDenseElements to something that doesn't
 crash.

---
 js/src/jsarray.cpp | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

(limited to 'js/src/jsarray.cpp')

diff --git a/js/src/jsarray.cpp b/js/src/jsarray.cpp
index 7af7c9800..159717fea 100644
--- a/js/src/jsarray.cpp
+++ b/js/src/jsarray.cpp
@@ -2361,6 +2361,22 @@ CanOptimizeForDenseStorage(HandleObject arr, uint32_t startingIndex, uint32_t co
            startingIndex + count <= arr->as<NativeObject>().getDenseInitializedLength();
 }
 
+static inline DenseElementResult
+CopyDenseElements(JSContext* cx, NativeObject* dst, NativeObject* src,
+                      uint32_t dstStart, uint32_t srcStart, uint32_t length)
+{
+    MOZ_ASSERT(dst->getDenseInitializedLength() == dstStart);
+    MOZ_ASSERT(src->getDenseInitializedLength() >= srcStart + length);
+    MOZ_ASSERT(dst->getDenseCapacity() >= dstStart + length);
+
+    dst->setDenseInitializedLength(dstStart + length);
+
+    const Value* vp = src->getDenseElements() + srcStart;
+    dst->initDenseElements(dstStart, vp, length);
+
+    return DenseElementResult::Success;
+}
+
 /* ES 2016 draft Mar 25, 2016 22.1.3.26. */
 bool
 js::array_splice(JSContext* cx, unsigned argc, Value* vp)
@@ -2459,7 +2475,9 @@ js::array_splice_impl(JSContext* cx, unsigned argc, Value* vp, bool returnValueI
 
                 /* Steps 10-11. */
                 DebugOnly<DenseElementResult> result =
-                    CopyBoxedOrUnboxedDenseElements(cx, arr, obj, 0, actualStart, actualDeleteCount);
+                    CopyDenseElements(cx, &arr->as<NativeObject>(), 
+					                  &obj->as<NativeObject>(), 0, 
+									  actualStart, actualDeleteCount);
                 MOZ_ASSERT(result.value == DenseElementResult::Success);
 
                 /* Step 12 (implicit). */
@@ -2827,7 +2845,7 @@ ArraySliceOrdinary(JSContext* cx, HandleObject obj, uint32_t length, uint32_t be
 
         if (count) {
             DebugOnly<DenseElementResult> result =
-                CopyBoxedOrUnboxedDenseElements(cx, narr, obj, 0, begin, count);
+                CopyDenseElements(cx, &narr->as<NativeObject>(), &obj->as<NativeObject>(), 0, begin, count);
             MOZ_ASSERT(result.value == DenseElementResult::Success);
         }
         arr.set(narr);
@@ -2968,7 +2986,7 @@ ArraySliceDenseKernel(JSContext* cx, ArrayObject* arr, int32_t beginArg, int32_t
         if (count) {
             if (!result->ensureElements(cx, count))
                 return false;
-            CopyBoxedOrUnboxedDenseElements(cx, result, arr, 0, begin, count);
+            CopyDenseElements(cx, &result->as<NativeObject>(), &arr->as<NativeObject>(), 0, begin, count);
         }
     }
 
-- 
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