[MERGE #5163 @pleath] [MSFT 16846859] Make ScopeSlots::Is handle null slot in FrameDisplay

pleath · pleath · commit 4f21511da453 · 2018-05-15T16:25:21.000-07:00
Merge pull request #5163 from pleath:16846859
diff --git a/lib/Runtime/Base/FunctionBody.h b/lib/Runtime/Base/FunctionBody.h
@@ -3380,6 +3380,12 @@ namespace Js
         // CONSIDER: Use TaggedInt instead of range of slot count to distinguish slot array with others.
         static bool Is(void* object)
         {
+            if (object == nullptr)
+            {
+                // Null slot in a frame where nothing is captured and the scope object has been eliminated
+                // by stack args optimization.
+                return false;
+            }
             size_t slotCount = *((size_t*)object);
             if(slotCount <= MaxEncodedSlotCount)
             {

Original file line number	Diff line number	Diff line change
`@@ -3380,6 +3380,12 @@ namespace Js`
`3380`	`3380`	`// CONSIDER: Use TaggedInt instead of range of slot count to distinguish slot array with others.`
`3381`	`3381`	`static bool Is(void* object)`
`3382`	`3382`	`{`
	`3383`	`+ if (object == nullptr)`
	`3384`	`+ {`
	`3385`	`+ // Null slot in a frame where nothing is captured and the scope object has been eliminated`
	`3386`	`+ // by stack args optimization.`
	`3387`	`+ return false;`
	`3388`	`+ }`
`3383`	`3389`	`size_t slotCount = ((size_t)object);`
`3384`	`3390`	`if(slotCount <= MaxEncodedSlotCount)`
`3385`	`3391`	`{`