another bug description

git-svn-id: svn+q:///qpdf/trunk@974 71b93d88-0707-0410-a8cf-f5a4172ac649

TODO

@@ -1,3 +1,47 @@
+Bug
+===
+
+ * There is a memory leak that happens whenever object A refers to
+   object B which refers back to object A.  We have the following
+   pattern:
+
+   #include "PointerHolder.hh"
+
+   class A
+   {
+     public:
+       PointerHolder<A> a;
+   };
+
+   int main()
+   {
+       A a1;
+       a1.a = new A();
+       a1.a.getPointer()->a = new A();
+       a1.a.getPointer()->a.getPointer()->a = a1.a;
+       return 0;
+   }
+
+   In order to fix this, we have to explicitly break circular
+   references, but we have to do this at a time that doesn't
+   completely destroy performance.
+
+   To debug, configure with
+
+   ./configure --disable-shared --disable-test-compare-images \
+      CFLAGS=-g CXXFLAGS=-g
+
+   Current code causes test failures.  linearize segfaults on
+   hybrid-xref.pdf, and the test suite fails in various places.  Maybe
+   because we don't do any kind of loop detection?
+
+   Use valgrind --leak-check=full to see leak details.
+
+   The file memory-leak.pdf is a minimal case that shows the problem.
+
+   Files in trace having tracing to show which objects haven't been
+   allocated.
+
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