Fix infinite loops in FPDF_GetFullName().

core/fpdfdoc/cpdf_formfield_unittest.cpp

Index: core/fpdfdoc/cpdf_formfield_unittest.cpp
diff --git a/core/fpdfdoc/cpdf_formfield_unittest.cpp b/core/fpdfdoc/cpdf_formfield_unittest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..33a21185cd1dd1bf8bba8299a97e8e488472ec80
--- /dev/null
+++ b/core/fpdfdoc/cpdf_formfield_unittest.cpp
@@ -0,0 +1,50 @@
+// Copyright 2016 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/fpdfapi/fpdf_parser/include/cpdf_dictionary.h"
+#include "core/fpdfapi/fpdf_parser/include/cpdf_indirect_object_holder.h"
+#include "core/fpdfdoc/include/cpdf_formfield.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+TEST(cpdf_formfield, FPDF_GetFullName) {
+  CFX_WideString name = FPDF_GetFullName(nullptr);
+  EXPECT_TRUE(name.IsEmpty());
+
+  CPDF_IndirectObjectHolder obj_holder;
+  CPDF_Dictionary* root = new CPDF_Dictionary;
+  obj_holder.AddIndirectObject(root);
+  root->SetAtName("T", "foo");
+  name = FPDF_GetFullName(root);
+  EXPECT_STREQ("foo", name.UTF8Encode().c_str());
+
+  CPDF_Dictionary* dict1 = new CPDF_Dictionary;
+  obj_holder.AddIndirectObject(dict1);
+  dict1->SetAtName("T", "bar");
+  root->SetAtReference("Parent", &obj_holder, dict1);
+  name = FPDF_GetFullName(root);
+  EXPECT_STREQ("bar.foo", name.UTF8Encode().c_str());
+
+  CPDF_Dictionary* dict2 = new CPDF_Dictionary;
+  obj_holder.AddIndirectObject(dict2);
+  dict1->SetAt("Parent", dict2);
+  name = FPDF_GetFullName(root);
+  EXPECT_STREQ("bar.foo", name.UTF8Encode().c_str());
+
+  CPDF_Dictionary* dict3 = new CPDF_Dictionary;
+  obj_holder.AddIndirectObject(dict3);
+  dict3->SetAtName("T", "qux");
+  dict2->SetAtReference("Parent", &obj_holder, dict3);
+  name = FPDF_GetFullName(root);
+  EXPECT_STREQ("qux.bar.foo", name.UTF8Encode().c_str());
+
+  dict3->SetAtReference("Parent", &obj_holder, root);
+  name = FPDF_GetFullName(root);
+  EXPECT_STREQ("qux.bar.foo", name.UTF8Encode().c_str());
+  name = FPDF_GetFullName(dict1);
+  EXPECT_STREQ("foo.qux.bar", name.UTF8Encode().c_str());
+  name = FPDF_GetFullName(dict2);
+  EXPECT_STREQ("bar.foo.qux", name.UTF8Encode().c_str());
+  name = FPDF_GetFullName(dict3);
+  EXPECT_STREQ("bar.foo.qux", name.UTF8Encode().c_str());
+}