From 89386daa9571add3bc30311dc0902f82a1148a4c Mon Sep 17 00:00:00 2001
From: Cameron Desrochers <cameron@moodycamel.com>
Date: Wed, 9 Oct 2019 18:27:33 +0000
Subject: [LLDB] Fix for synthetic children memory leak

The lifetime of a ValueObject and all its derivative ValueObjects (children, clones, etc.) is managed by a ClusterManager. These objects are only destroyed when every shared pointer to any of the managed objects in the cluster is destroyed. This means that no object in the cluster can store a shared pointer to another object in the cluster without creating a memory leak of the entire cluster. However, some of the synthetic children front-end implementations do exactly this; this patch fixes that.

Differential Revision: https://reviews.llvm.org/D68641

llvm-svn: 374195
---
 .../Language/CPlusPlus/LibStdcppUniquePointer.cpp  | 23 +++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

(limited to 'lldb/source/Plugins/Language/CPlusPlus/LibStdcppUniquePointer.cpp')

diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibStdcppUniquePointer.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibStdcppUniquePointer.cpp
index 3860f960cb3..84f9e57015f 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibStdcppUniquePointer.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibStdcppUniquePointer.cpp
@@ -39,9 +39,14 @@ public:
   bool GetSummary(Stream &stream, const TypeSummaryOptions &options);
 
 private:
-  ValueObjectSP m_ptr_obj;
-  ValueObjectSP m_obj_obj;
-  ValueObjectSP m_del_obj;
+  // The lifetime of a ValueObject and all its derivative ValueObjects
+  // (children, clones, etc.) is managed by a ClusterManager. These
+  // objects are only destroyed when every shared pointer to any of them
+  // is destroyed, so we must not store a shared pointer to any ValueObject
+  // derived from our backend ValueObject (since we're in the same cluster).
+  ValueObject* m_ptr_obj = nullptr;
+  ValueObject* m_obj_obj = nullptr;
+  ValueObject* m_del_obj = nullptr;
 
   ValueObjectSP GetTuple();
 };
@@ -92,17 +97,17 @@ bool LibStdcppUniquePtrSyntheticFrontEnd::Update() {
 
   ValueObjectSP ptr_obj = tuple_frontend->GetChildAtIndex(0);
   if (ptr_obj)
-    m_ptr_obj = ptr_obj->Clone(ConstString("pointer"));
+    m_ptr_obj = ptr_obj->Clone(ConstString("pointer")).get();
 
   ValueObjectSP del_obj = tuple_frontend->GetChildAtIndex(1);
   if (del_obj)
-    m_del_obj = del_obj->Clone(ConstString("deleter"));
+    m_del_obj = del_obj->Clone(ConstString("deleter")).get();
 
   if (m_ptr_obj) {
     Status error;
     ValueObjectSP obj_obj = m_ptr_obj->Dereference(error);
     if (error.Success()) {
-      m_obj_obj = obj_obj->Clone(ConstString("object"));
+      m_obj_obj = obj_obj->Clone(ConstString("object")).get();
     }
   }
 
@@ -114,11 +119,11 @@ bool LibStdcppUniquePtrSyntheticFrontEnd::MightHaveChildren() { return true; }
 lldb::ValueObjectSP
 LibStdcppUniquePtrSyntheticFrontEnd::GetChildAtIndex(size_t idx) {
   if (idx == 0)
-    return m_ptr_obj;
+    return m_ptr_obj->GetSP();
   if (idx == 1)
-    return m_del_obj;
+    return m_del_obj->GetSP();
   if (idx == 2)
-    return m_obj_obj;
+    return m_obj_obj->GetSP();
   return lldb::ValueObjectSP();
 }
 
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