SERVER-10554 Patch memory leak in aggregation

The issue was that empty documents are represented as a NULL pointer and
Value didn't ref count NULL pointers. This is fine for all public
interactions with Value, however MutableDocument can change the pointer
in-place when updating a nested field. This caused a leak when it
transitioned a Value from holding a non-refcounted NULL pointer to
holding a real pointer since MutableDocument/MutableValue didn't set the
refCount bit.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/mongo/dbtests/documenttests.cpp b/src/mongo/dbtests/documenttests.cpp
index c220c17abca..7017240a876 100644
--- a/src/mongo/dbtests/documenttests.cpp
+++ b/src/mongo/dbtests/documenttests.cpp
@@ -167,6 +167,22 @@ namespace DocumentTests {
                 ASSERT( md.peek()["c"].missing() );
                 assertRoundTrips( md.peek() );
 
+                // Set a nested field using []
+                md["x"]["y"]["z"] = Value("nested");
+                ASSERT_EQUALS(md.peek()["x"]["y"]["z"], Value("nested"));
+
+                // Set a nested field using setNestedField
+                FieldPath xxyyzz = string("xx.yy.zz");
+                md.setNestedField(xxyyzz, Value("nested"));
+                ASSERT_EQUALS(md.peek().getNestedField(xxyyzz), Value("nested") );
+
+                // Set a nested fields through an existing empty document
+                md["xxx"] = Value(Document());
+                md["xxx"]["yyy"] = Value(Document());
+                FieldPath xxxyyyzzz = string("xxx.yyy.zzz");
+                md.setNestedField(xxxyyyzzz, Value("nested"));
+                ASSERT_EQUALS(md.peek().getNestedField(xxxyyyzzz), Value("nested") );
+
                 // Make sure nothing moved
                 ASSERT_EQUALS(apos, md.peek().positionOf("a"));
                 ASSERT_EQUALS(bpos, md.peek().positionOf("c"));