Nice patch by Gang Hu, Heming Cui and Junfeng Yang fixing a memory

leak in KLEE.

From Gang Hu: "The memory leak is caused by two reasons.  First, the
MemoryObject objects are not freed, until the MemoryManager is
destroyed.  Second, when KLEE allocates a non-fixed MemoryObject
object, KLEE also allocates a block of memory which is the same as the
object's size. This block of memory is never freed.  So, this patch
generally does reference counting on the MemoryObject objects, and
frees them as soon as the reference count drops to zero."

Many thanks to Paul Marinescu as well, who tested this patch
thoroughly on the Coreutils benchmarks.  On 1h runs, the memory
consumption typically goes down by 1-5%, but some applications which
see more significant gains.



git-svn-id: https://llvm.org/svn/llvm-project/klee/trunk@148402 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 91 insertions, 11 deletions

diff --git a/lib/Core/ExecutionState.cpp b/lib/Core/ExecutionState.cpp
index c6a2cad4..db685639 100644
--- a/lib/Core/ExecutionState.cpp
+++ b/lib/Core/ExecutionState.cpp
@@ -86,9 +86,46 @@ ExecutionState::ExecutionState(const std::vector<ref<Expr> > &assumptions)
 }
 
 ExecutionState::~ExecutionState() {
+  for (unsigned int i=0; i<symbolics.size(); i++)
+  {
+    const MemoryObject *mo = symbolics[i].first;
+    assert(mo->refCount > 0);
+    mo->refCount--;
+    if (mo->refCount == 0)
+      delete mo;
+  }
+
   while (!stack.empty()) popFrame();
 }
 
+ExecutionState::ExecutionState(const ExecutionState& state)
+  : fnAliases(state.fnAliases),
+    fakeState(state.fakeState),
+    underConstrained(state.underConstrained),
+    depth(state.depth),
+    pc(state.pc),
+    prevPC(state.prevPC),
+    stack(state.stack),
+    constraints(state.constraints),
+    queryCost(state.queryCost),
+    weight(state.weight),
+    addressSpace(state.addressSpace),
+    pathOS(state.pathOS),
+    symPathOS(state.symPathOS),
+    instsSinceCovNew(state.instsSinceCovNew),
+    coveredNew(state.coveredNew),
+    forkDisabled(state.forkDisabled),
+    coveredLines(state.coveredLines),
+    ptreeNode(state.ptreeNode),
+    symbolics(state.symbolics),
+    arrayNames(state.arrayNames),
+    shadowObjects(state.shadowObjects),
+    incomingBBIndex(state.incomingBBIndex)
+{
+  for (unsigned int i=0; i<symbolics.size(); i++)
+    symbolics[i].first->refCount++;
+}
+
 ExecutionState *ExecutionState::branch() {
   depth++;
 
@@ -114,6 +151,10 @@ void ExecutionState::popFrame() {
   stack.pop_back();
 }
 
+void ExecutionState::addSymbolic(const MemoryObject *mo, const Array *array) { 
+  mo->refCount++;
+  symbolics.push_back(std::make_pair(mo, array));
+}
 ///
 
 std::string ExecutionState::getFnAlias(std::string fn) {
diff --git a/lib/Core/Memory.cpp b/lib/Core/Memory.cpp
index d54264a3..7b3655f8 100644
--- a/lib/Core/Memory.cpp
+++ b/lib/Core/Memory.cpp
@@ -17,6 +17,7 @@
 #include "klee/util/BitArray.h"
 
 #include "ObjectHolder.h"
+#include "MemoryManager.h"
 
 #include <llvm/Function.h>
 #include <llvm/Instruction.h>
@@ -63,6 +64,8 @@ ObjectHolder &ObjectHolder::operator=(const ObjectHolder &b) {
 int MemoryObject::counter = 0;
 
 MemoryObject::~MemoryObject() {
+  if (parent)
+    parent->markFreed(this);
 }
 
 void MemoryObject::getAllocInfo(std::string &result) const {
@@ -100,6 +103,7 @@ ObjectState::ObjectState(const MemoryObject *mo)
     updates(0, 0),
     size(mo->size),
     readOnly(false) {
+  mo->refCount++;
   if (!UseConstantArrays) {
     // FIXME: Leaked.
     static unsigned id = 0;
@@ -120,6 +124,7 @@ ObjectState::ObjectState(const MemoryObject *mo, const Array *array)
     updates(array, 0),
     size(mo->size),
     readOnly(false) {
+  mo->refCount++;
   makeSymbolic();
 }
 
@@ -135,6 +140,8 @@ ObjectState::ObjectState(const ObjectState &os)
     size(os.size),
     readOnly(false) {
   assert(!os.readOnly && "no need to copy read only object?");
+  if (object)
+    object->refCount++;
 
   if (os.knownSymbolics) {
     knownSymbolics = new ref<Expr>[size];
@@ -150,6 +157,16 @@ ObjectState::~ObjectState() {
   if (flushMask) delete flushMask;
   if (knownSymbolics) delete[] knownSymbolics;
   delete[] concreteStore;
+
+  if (object)
+  {
+    assert(object->refCount > 0);
+    object->refCount--;
+    if (object->refCount == 0)
+    {
+      delete object;
+    }
+  }
 }
 
 /***/
diff --git a/lib/Core/Memory.h b/lib/Core/Memory.h
index 9ce8e09b..637f8772 100644
--- a/lib/Core/Memory.h
+++ b/lib/Core/Memory.h
@@ -30,9 +30,12 @@ class Solver;
 
 class MemoryObject {
   friend class STPBuilder;
+  friend class ObjectState;
+  friend class ExecutionState;
 
 private:
   static int counter;
+  mutable unsigned refCount;
 
 public:
   unsigned id;
@@ -50,6 +53,8 @@ public:
   bool fake_object;
   bool isUserSpecified;
 
+  MemoryManager *parent;
+
   /// "Location" for which this memory object was allocated. This
   /// should be either the allocating instruction or the global object
   /// it was allocated for (or whatever else makes sense).
@@ -69,17 +74,21 @@ public:
   // XXX this is just a temp hack, should be removed
   explicit
   MemoryObject(uint64_t _address) 
-    : id(counter++),
+    : refCount(0),
+      id(counter++), 
       address(_address),
       size(0),
       isFixed(true),
+      parent(NULL),
       allocSite(0) {
   }
 
   MemoryObject(uint64_t _address, unsigned _size, 
                bool _isLocal, bool _isGlobal, bool _isFixed,
-               const llvm::Value *_allocSite) 
-    : id(counter++),
+               const llvm::Value *_allocSite,
+               MemoryManager *_parent)
+    : refCount(0), 
+      id(counter++),
       address(_address),
       size(_size),
       name("unnamed"),
@@ -88,6 +97,7 @@ public:
       isFixed(_isFixed),
       fake_object(false),
       isUserSpecified(false),
+      parent(_parent), 
       allocSite(_allocSite) {
   }
 
diff --git a/lib/Core/MemoryManager.cpp b/lib/Core/MemoryManager.cpp
index 79fbcecf..06c234a2 100644
--- a/lib/Core/MemoryManager.cpp
+++ b/lib/Core/MemoryManager.cpp
@@ -25,8 +25,10 @@ using namespace klee;
 
 MemoryManager::~MemoryManager() { 
   while (!objects.empty()) {
-    MemoryObject *mo = objects.back();
-    objects.pop_back();
+    MemoryObject *mo = *objects.begin();
+    if (!mo->isFixed)
+      free((void *)mo->address);
+    objects.erase(mo);
     delete mo;
   }
 }
@@ -44,8 +46,8 @@ MemoryObject *MemoryManager::allocate(uint64_t size, bool isLocal,
   
   ++stats::allocations;
   MemoryObject *res = new MemoryObject(address, size, isLocal, isGlobal, false,
-                                       allocSite);
-  objects.push_back(res);
+                                       allocSite, this);
+  objects.insert(res);
   return res;
 }
 
@@ -62,11 +64,20 @@ MemoryObject *MemoryManager::allocateFixed(uint64_t address, uint64_t size,
 
   ++stats::allocations;
   MemoryObject *res = new MemoryObject(address, size, false, true, true,
-                                       allocSite);
-  objects.push_back(res);
+                                       allocSite, this);
+  objects.insert(res);
   return res;
 }
 
 void MemoryManager::deallocate(const MemoryObject *mo) {
   assert(0);
 }
+
+void MemoryManager::markFreed(MemoryObject *mo) {
+  if (objects.find(mo) != objects.end())
+  {
+    if (!mo->isFixed)
+      free((void *)mo->address);
+    objects.erase(mo);
+  }
+}
diff --git a/lib/Core/MemoryManager.h b/lib/Core/MemoryManager.h
index adb2ba22..f398db62 100644
--- a/lib/Core/MemoryManager.h
+++ b/lib/Core/MemoryManager.h
@@ -10,7 +10,7 @@
 #ifndef KLEE_MEMORYMANAGER_H
 #define KLEE_MEMORYMANAGER_H
 
-#include <vector>
+#include <set>
 #include <stdint.h>
 
 namespace llvm {
@@ -22,7 +22,7 @@ namespace klee {
 
   class MemoryManager {
   private:
-    typedef std::vector<MemoryObject*> objects_ty;
+    typedef std::set<MemoryObject*> objects_ty;
     objects_ty objects;
 
   public:
@@ -34,6 +34,7 @@ namespace klee {
     MemoryObject *allocateFixed(uint64_t address, uint64_t size,
                                 const llvm::Value *allocSite);
     void deallocate(const MemoryObject *mo);
+    void markFreed(MemoryObject *mo);
   };
 
 } // End klee namespace