Merge to XFA: Fix potential UAF in ConcatInPlace.

core/src/fxcrt/fx_basic_bstring_unittest.cpp

 // Copyright 2014 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 "testing/gtest/include/gtest/gtest.h"
 #include "../../../testing/fx_string_testhelpers.h"
 #include "../../include/fxcrt/fx_basic.h"
 
 TEST(fxcrt, ByteStringOperatorSubscript) {
     // CFX_ByteString includes the NUL terminator for non-empty strings.
@@ skipping 270 matching lines @@
   assigned_nullptr_string = (FX_LPCSTR)nullptr;
   EXPECT_EQ(assigned_nullptr_string.GetPtr(), nullptr);
   EXPECT_EQ(assigned_nullptr_string.GetLength(), 0);
   EXPECT_TRUE(assigned_nullptr_string.IsEmpty());
   EXPECT_EQ(null_string, assigned_nullptr_string);
 
   CFX_ByteStringC non_null_string("a");
   EXPECT_NE(null_string, non_null_string);
 }
 
+TEST(fxcrt, ByteStringConcatInPlace) {
+    CFX_ByteString fred;
+    fred.ConcatInPlace(4, "FRED");
+    EXPECT_EQ("FRED", fred);
+
+    fred.ConcatInPlace(2, "DY");
+    EXPECT_EQ("FREDDY", fred);
+
+    fred.Delete(3, 3);
+    EXPECT_EQ("FRE", fred);
+
+    fred.ConcatInPlace(1, "D");
+    EXPECT_EQ("FRED", fred);
+
+    CFX_ByteString copy = fred;
+    fred.ConcatInPlace(2, "DY");
+    EXPECT_EQ("FREDDY", fred);
+    EXPECT_EQ("FRED", copy);
+
+    // Test invalid arguments.
+    copy = fred;
+    fred.ConcatInPlace(-6, "freddy");
+    CFX_ByteString not_aliased("xxxxxx");
+    EXPECT_EQ("FREDDY", fred);
+    EXPECT_EQ("xxxxxx", not_aliased);
+}
+
 TEST(fxcrt, ByteStringCNotNull) {
   CFX_ByteStringC string3("abc");
   CFX_ByteStringC string6("abcdef");
   CFX_ByteStringC alternate_string3("abcdef", 3);
   CFX_ByteStringC embedded_nul_string7("abc\0def", 7);
   CFX_ByteStringC illegal_string7("abcdef", 7);
 
   EXPECT_EQ(3, string3.GetLength());
   EXPECT_EQ(6, string6.GetLength());
   EXPECT_EQ(3, alternate_string3.GetLength());
@@ skipping 268 matching lines @@
     const char* c_string2 = "hellp";
     const char* c_string3 = "hellod";
     EXPECT_TRUE(byte_string_c != c_string1);
     EXPECT_TRUE(byte_string_c != c_string2);
     EXPECT_TRUE(byte_string_c != c_string3);
 
     EXPECT_TRUE(c_string1 != byte_string_c);
     EXPECT_TRUE(c_string2 != byte_string_c);
     EXPECT_TRUE(c_string3 != byte_string_c);
 }