Bug fix: treat old generations of reused objects as null

1 files changed, 25 insertions, 0 deletions

diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index 3718eb7e..a089a6c2 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -706,6 +706,19 @@ QPDF::read_xref(qpdf_offset_t xref_offset)
     // We no longer need the deleted_objects table, so go ahead and clear it out to make sure we
     // never depend on its being set.
     m->deleted_objects.clear();
+
+    // Make sure we keep only the highest generation for any object.
+    QPDFObjGen::set to_delete;
+    QPDFObjGen last_og;
+    for (auto const& og: m->xref_table) {
+        if (og.first.getObj() == last_og.getObj()) {
+            to_delete.emplace(last_og);
+        }
+        last_og = og.first;
+    }
+    for (auto const& og: to_delete) {
+        removeObject(og);
+    }
 }
 
 bool
@@ -1979,6 +1992,18 @@ QPDF::replaceObject(QPDFObjGen const& og, QPDFObjectHandle oh)
 }
 
 void
+QPDF::removeObject(QPDFObjGen const& og)
+{
+    auto null = QPDFObjectHandle::newNull();
+    m->xref_table.erase(og);
+    if (isCached(og)) {
+        // Take care of any object handles that may be floating around.
+        replaceObject(og, null);
+    }
+    m->obj_cache.erase(og);
+}
+
+void
 QPDF::replaceReserved(QPDFObjectHandle reserved, QPDFObjectHandle replacement)
 {
     QTC::TC("qpdf", "QPDF replaceReserved");