comment on memory leak fix

git-svn-id: svn+q:///qpdf/trunk@979 71b93d88-0707-0410-a8cf-f5a4172ac649

comment on memory leak fix
git-svn-id: svn+q:///qpdf/trunk@979 71b93d88-0707-0410-a8cf-f5a4172ac649
Jay Berkenbilt
1 parent 21753001
Showing 2 changed files with 18 additions and 0 deletions
libqpdf/QPDF.cc
libqpdf/QPDFObjectHandle.cc
@@ -277,6 +277,20 @@ QPDF::QPDF() :
 QPDF::~QPDF()
 {
+    // If two objects are mutually referential (through each object
+    // having an array or dictionary that contains an indirect
+    // reference to the other), the circular references in the
+    // PointerHolder objects will prevent the objects from being
+    // deleted.  Walk through all objects in the object cache, which
+    // is those objects that we read from the file, and break all
+    // resolved references.  At this point, obviously no one is still
+    // using the QPDF object, but we'll explicitly clear the xref
+    // table anyway just to prevent any possibility of resolve()
+    // succeeding.  Note that we can't break references like this at
+    // any time when the QPDF object is active.  If we do, the next
+    // reference will reread the object from the file, which would
+    // have the effect of undoing any modifications that may have been
+    // made to any of the objects.
     this->xref_table.clear();
     for (std::map<ObjGen, ObjCache>::iterator iter = this->obj_cache.begin();
 	 iter != obj_cache.end(); ++iter)
@@ -44,6 +44,10 @@ QPDFObjectHandle::QPDFObjectHandle(QPDFObject* data) :
 void
 QPDFObjectHandle::releaseResolved()
 {
+    // Recursively break any resolved references to indirect objects.
+    // Do not cross over indirect object boundaries to avoid an
+    // infinite loop.  This method may only be called during final
+    // destruction.  See comments in QPDF::~QPDF().
     if (isIndirect())
     {
 	if (this->obj.getPointer())