Merge to XFA: Add missing operators for CFX_xxxString combo patch.

This pulls in:
Review URL: https://codereview.chromium.org/1099193002
Review URL: https://codereview.chromium.org/1090303003
Review URL: https://codereview.chromium.org/1084293003
Review URL: https://codereview.chromium.org/1099213002

Plus one fix to an XFA file to fix compilation.

TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1095893005

9 files changed, 245 insertions, 60 deletions

diff --git a/core/include/fxcrt/fx_string.h b/core/include/fxcrt/fx_string.h
index 70f64932c8..1efb814b08 100644
--- a/core/include/fxcrt/fx_string.h
+++ b/core/include/fxcrt/fx_string.h
@@ -7,6 +7,8 @@
 #ifndef _FX_STRING_H_
 #define _FX_STRING_H_
 
+#include <algorithm>
+
 #include "fx_memory.h"
 
 class CFX_ByteStringC;
@@ -21,7 +23,7 @@ class CFX_WideStringL;
 
 // An immutable string with caller-provided storage which must outlive the
 // string itself.
-class CFX_ByteStringC 
+class CFX_ByteStringC
 {
 public:
     typedef FX_CHAR value_type;
@@ -100,7 +102,6 @@ public:
     {
         return 	str.m_Length != m_Length || FXSYS_memcmp32(str.m_Ptr, m_Ptr, m_Length) != 0;
     }
-#define FXBSTR_ID(c1, c2, c3, c4) ((c1 << 24) | (c2 << 16) | (c3 << 8) | (c4))
 
     FX_DWORD		GetID(FX_STRSIZE start_pos = 0) const;
 
@@ -124,11 +125,6 @@ public:
         return m_Length == 0;
     }
 
-    operator		FX_LPCBYTE() const
-    {
-        return m_Ptr;
-    }
-
     FX_BYTE			GetAt(FX_STRSIZE index) const
     {
         return m_Ptr[index];
@@ -147,13 +143,23 @@ public:
         }
         return CFX_ByteStringC(m_Ptr + index, count);
     }
-protected:
 
-    FX_LPCBYTE		m_Ptr;
+    const FX_BYTE& operator[] (size_t index) const
+    {
+        return m_Ptr[index];
+    }
+
+    bool operator< (const CFX_ByteStringC& that) const
+    {
+        int result = memcmp(m_Ptr, that.m_Ptr, std::min(m_Length, that.m_Length));
+        return result < 0 || (result == 0 && m_Length < that.m_Length);
+    }
 
+protected:
+    FX_LPCBYTE		m_Ptr;
     FX_STRSIZE		m_Length;
-private:
 
+private:
     void*			operator new (size_t) throw()
     {
         return NULL;
@@ -161,6 +167,7 @@ private:
 };
 typedef const CFX_ByteStringC& FX_BSTR;
 #define FX_BSTRC(str) CFX_ByteStringC(str, sizeof str-1)
+#define FXBSTR_ID(c1, c2, c3, c4) ((c1 << 24) | (c2 << 16) | (c3 << 8) | (c4))
 struct CFX_StringData {
 
     long		m_nRefs;
@@ -261,6 +268,12 @@ public:
         return !operator==(str);
     }
 
+    bool operator< (const CFX_ByteString& str) const
+    {
+        int result = FXSYS_memcmp32(c_str(), str.c_str(), std::min(GetLength(), str.GetLength()));
+        return result < 0 || (result == 0 && GetLength() < str.GetLength());
+    }
+
     void					Empty();
 
     const CFX_ByteString&	operator = (FX_LPCSTR str);
@@ -428,7 +441,7 @@ inline CFX_ByteString operator + (FX_BSTR str1, const CFX_ByteString& str2)
 {
     return CFX_ByteString(str1, str2);
 }
-class CFX_WideStringC 
+class CFX_WideStringC
 {
 public:
     typedef FX_WCHAR value_type;
@@ -550,13 +563,23 @@ public:
         }
         return CFX_WideStringC(m_Ptr + m_Length - count, count);
     }
-protected:
 
-    FX_LPCWSTR		m_Ptr;
+    const FX_WCHAR& operator[] (size_t index) const
+    {
+        return m_Ptr[index];
+    }
 
+    bool operator< (const CFX_WideStringC& that) const
+    {
+        int result = wmemcmp(m_Ptr, that.m_Ptr, std::min(m_Length, that.m_Length));
+        return result < 0 || (result == 0 && m_Length < that.m_Length);
+     }
+
+protected:
+    FX_LPCWSTR		m_Ptr;
     FX_STRSIZE		m_Length;
-private:
 
+private:
     void*			operator new (size_t) throw()
     {
         return NULL;
@@ -646,6 +669,11 @@ public:
 
     const CFX_WideString&	operator += (const CFX_WideStringC& str);
 
+    bool operator< (const CFX_WideString& str) const {
+        int result = wmemcmp(c_str(), str.c_str(), std::min(GetLength(), str.GetLength()));
+        return result < 0 || (result == 0 && GetLength() < str.GetLength());
+    }
+
     FX_WCHAR				GetAt(FX_STRSIZE nIndex) const
     {
         return m_pData ? m_pData->m_String[nIndex] : 0;
diff --git a/core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp b/core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp
index 612b0e3716..4ba65f2ccb 100644
--- a/core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp
+++ b/core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp
@@ -427,7 +427,7 @@ void CPDF_GeneralStateData::SetBlendMode(FX_BSTR blend_mode)
     if (blend_mode.GetLength() > 15) {
         return;
     }
-    FXSYS_memcpy32(m_BlendMode, (FX_LPCBYTE)blend_mode, blend_mode.GetLength());
+    FXSYS_memcpy32(m_BlendMode, blend_mode.GetPtr(), blend_mode.GetLength());
     m_BlendMode[blend_mode.GetLength()] = 0;
     m_BlendType = ::GetBlendType(blend_mode);
 }
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index b45e23467f..cc517dd4c2 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -2562,7 +2562,7 @@ FX_BOOL CPDF_SyntaxParser::SearchWord(FX_BSTR tag, FX_BOOL bWholeWord, FX_BOOL b
     if (!bForward) {
         offset = taglen - 1;
     }
-    FX_LPCBYTE tag_data = tag;
+    FX_LPCBYTE tag_data = tag.GetPtr();
     FX_BYTE byte;
     while (1) {
         if (bForward) {
@@ -2599,7 +2599,7 @@ FX_BOOL CPDF_SyntaxParser::SearchWord(FX_BSTR tag, FX_BOOL bWholeWord, FX_BOOL b
                 }
             }
             FX_FILESIZE startpos = bForward ? pos - taglen + 1 : pos;
-            if (!bWholeWord || IsWholeWord(startpos, limit, tag, taglen)) {
+            if (!bWholeWord || IsWholeWord(startpos, limit, tag.GetPtr(), taglen)) {
                 m_Pos = startpos;
                 return TRUE;
             }
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
index bbfd4cc680..df154eae90 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
@@ -51,7 +51,7 @@ CPDF_SimpleParser::CPDF_SimpleParser(FX_LPCBYTE pData, FX_DWORD dwSize)
 }
 CPDF_SimpleParser::CPDF_SimpleParser(FX_BSTR str)
 {
-    m_pData = str;
+    m_pData = str.GetPtr();
     m_dwSize = str.GetLength();
     m_dwCurPos = 0;
 }
@@ -198,7 +198,7 @@ FX_BOOL CPDF_SimpleParser::SearchToken(FX_BSTR token)
 {
     int token_len = token.GetLength();
     while (m_dwCurPos < m_dwSize - token_len) {
-        if (FXSYS_memcmp32(m_pData + m_dwCurPos, token, token_len) == 0) {
+        if (FXSYS_memcmp32(m_pData + m_dwCurPos, token.GetPtr(), token_len) == 0) {
             break;
         }
         m_dwCurPos ++;
diff --git a/core/src/fxcrt/fx_basic_bstring.cpp b/core/src/fxcrt/fx_basic_bstring.cpp
index ea9ca85021..cda7d1fdd7 100644
--- a/core/src/fxcrt/fx_basic_bstring.cpp
+++ b/core/src/fxcrt/fx_basic_bstring.cpp
@@ -276,7 +276,7 @@ bool CFX_ByteString::EqualNoCase(FX_BSTR str) const
         return false;
     }
     FX_LPCBYTE pThis = (FX_LPCBYTE)m_pData->m_String;
-    FX_LPCBYTE pThat = (FX_LPCBYTE)str;
+    FX_LPCBYTE pThat = str.GetPtr();
     for (FX_STRSIZE i = 0; i < len; i ++) {
         if ((*pThis) != (*pThat)) {
             FX_BYTE bThis = *pThis;
diff --git a/core/src/fxcrt/fx_basic_bstring_unittest.cpp b/core/src/fxcrt/fx_basic_bstring_unittest.cpp
index 53427e3650..57cfc8047e 100644
--- a/core/src/fxcrt/fx_basic_bstring_unittest.cpp
+++ b/core/src/fxcrt/fx_basic_bstring_unittest.cpp
@@ -6,6 +6,45 @@
 #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.
+    CFX_ByteString abc("abc");
+    EXPECT_EQ('a', abc[0]);
+    EXPECT_EQ('b', abc[1]);
+    EXPECT_EQ('c', abc[2]);
+    EXPECT_EQ(0, abc[3]);
+}
+
+TEST(fxcrt, ByteStringOperatorLT) {
+    CFX_ByteString empty;
+    CFX_ByteString a("a");
+    CFX_ByteString abc("abc");
+    CFX_ByteString def("def");
+
+    EXPECT_FALSE(empty < empty);
+    EXPECT_FALSE(a < a);
+    EXPECT_FALSE(abc < abc);
+    EXPECT_FALSE(def < def);
+
+    EXPECT_TRUE(empty < a);
+    EXPECT_FALSE(a < empty);
+
+    EXPECT_TRUE(empty < abc);
+    EXPECT_FALSE(abc < empty);
+
+    EXPECT_TRUE(empty < def);
+    EXPECT_FALSE(def < empty);
+
+    EXPECT_TRUE(a < abc);
+    EXPECT_FALSE(abc < a);
+
+    EXPECT_TRUE(a < def);
+    EXPECT_FALSE(def < a);
+
+    EXPECT_TRUE(abc < def);
+    EXPECT_FALSE(def < abc);
+}
+
 TEST(fxcrt, ByteStringCNull) {
   CFX_ByteStringC null_string;
   EXPECT_EQ(null_string.GetPtr(), nullptr);
@@ -190,3 +229,42 @@ TEST(fxcrt, ByteStringCGetAt) {
   EXPECT_EQ('\0', embedded_nul_string.GetAt(2));
   EXPECT_EQ('c', embedded_nul_string.GetAt(3));
 }
+
+TEST(fxcrt, ByteStringCOperatorSubscript) {
+    // CFX_ByteStringC includes the NUL terminator for non-empty strings.
+    CFX_ByteStringC abc("abc");
+    EXPECT_EQ('a', abc[0]);
+    EXPECT_EQ('b', abc[1]);
+    EXPECT_EQ('c', abc[2]);
+    EXPECT_EQ(0, abc[3]);
+}
+
+TEST(fxcrt, ByteStringCOperatorLT) {
+    CFX_ByteStringC empty;
+    CFX_ByteStringC a("a");
+    CFX_ByteStringC abc("abc");
+    CFX_ByteStringC def("def");
+
+    EXPECT_FALSE(empty < empty);
+    EXPECT_FALSE(a < a);
+    EXPECT_FALSE(abc < abc);
+    EXPECT_FALSE(def < def);
+
+    EXPECT_TRUE(empty < a);
+    EXPECT_FALSE(a < empty);
+
+    EXPECT_TRUE(empty < abc);
+    EXPECT_FALSE(abc < empty);
+
+    EXPECT_TRUE(empty < def);
+    EXPECT_FALSE(def < empty);
+
+    EXPECT_TRUE(a < abc);
+    EXPECT_FALSE(abc < a);
+
+    EXPECT_TRUE(a < def);
+    EXPECT_FALSE(def < a);
+
+    EXPECT_TRUE(abc < def);
+    EXPECT_FALSE(def < abc);
+}
diff --git a/core/src/fxcrt/fx_basic_buffer.cpp b/core/src/fxcrt/fx_basic_buffer.cpp
index bb8466debe..eb5246acec 100644
--- a/core/src/fxcrt/fx_basic_buffer.cpp
+++ b/core/src/fxcrt/fx_basic_buffer.cpp
@@ -143,7 +143,7 @@ CFX_ByteStringC CFX_BinaryBuf::GetByteString() const
 }
 CFX_ByteTextBuf& CFX_ByteTextBuf::operator << (FX_BSTR lpsz)
 {
-    AppendBlock((FX_LPCBYTE)lpsz, lpsz.GetLength());
+    AppendBlock(lpsz.GetPtr(), lpsz.GetLength());
     return *this;
 }
 CFX_ByteTextBuf& CFX_ByteTextBuf::operator << (int i)
@@ -174,7 +174,7 @@ CFX_ByteTextBuf& CFX_ByteTextBuf::operator << (const CFX_ByteTextBuf& buf)
 }
 void CFX_ByteTextBuf::operator =(const CFX_ByteStringC& str)
 {
-    CopyData((FX_LPCBYTE)str, str.GetLength());
+    CopyData(str.GetPtr(), str.GetLength());
 }
 void CFX_WideTextBuf::AppendChar(FX_WCHAR ch)
 {
@@ -285,10 +285,10 @@ CFX_ArchiveSaver& CFX_ArchiveSaver::operator << (FX_BSTR bstr)
     int len = bstr.GetLength();
     if (m_pStream) {
         m_pStream->WriteBlock(&len, sizeof(int));
-        m_pStream->WriteBlock(bstr, len);
+        m_pStream->WriteBlock(bstr.GetPtr(), len);
     } else {
         m_SavingBuf.AppendBlock(&len, sizeof(int));
-        m_SavingBuf.AppendBlock(bstr, len);
+        m_SavingBuf.AppendBlock(bstr.GetPtr(), len);
     }
     return *this;
 }
@@ -488,7 +488,7 @@ FX_INT32 IFX_BufferArchive::AppendDWord(FX_DWORD i)
 }
 FX_INT32 IFX_BufferArchive::AppendString(FX_BSTR lpsz)
 {
-    return AppendBlock((FX_LPCBYTE)lpsz, lpsz.GetLength());
+    return AppendBlock(lpsz.GetPtr(), lpsz.GetLength());
 }
 CFX_FileBufferArchive::CFX_FileBufferArchive(FX_STRSIZE size)
     : IFX_BufferArchive(size)
diff --git a/core/src/fxcrt/fx_basic_maps.cpp b/core/src/fxcrt/fx_basic_maps.cpp
index e85d35e4ac..8ae44ce6a0 100644
--- a/core/src/fxcrt/fx_basic_maps.cpp
+++ b/core/src/fxcrt/fx_basic_maps.cpp
@@ -352,7 +352,7 @@ inline FX_DWORD CFX_MapByteStringToPtr::HashKey(FX_BSTR key) const
 {
     FX_DWORD nHash = 0;
     int len = key.GetLength();
-    FX_LPCBYTE buf = key;
+    FX_LPCBYTE buf = key.GetPtr();
     for (int i = 0; i < len; i ++) {
         nHash = (nHash << 5) + nHash + buf[i];
     }
@@ -518,7 +518,7 @@ void CFX_CMapByteStringToPtr::SetAt(FX_BSTR key, void* value)
     int size = m_Buffer.GetSize();
     for (index = 0; index < size; index ++) {
         _CompactString* pKey = (_CompactString*)m_Buffer.GetAt(index);
-        if (!_CompactStringSame(pKey, (FX_LPCBYTE)key, key_len)) {
+        if (!_CompactStringSame(pKey, key.GetPtr(), key_len)) {
             continue;
         }
         *(void**)(pKey + 1) = value;
@@ -529,19 +529,19 @@ void CFX_CMapByteStringToPtr::SetAt(FX_BSTR key, void* value)
         if (pKey->m_CompactLen) {
             continue;
         }
-        _CompactStringStore(pKey, (FX_LPCBYTE)key, key_len);
+        _CompactStringStore(pKey, key.GetPtr(), key_len);
         *(void**)(pKey + 1) = value;
         return;
     }
     _CompactString* pKey = (_CompactString*)m_Buffer.Add();
-    _CompactStringStore(pKey, (FX_LPCBYTE)key, key_len);
+    _CompactStringStore(pKey, key.GetPtr(), key_len);
     *(void**)(pKey + 1) = value;
 }
 void CFX_CMapByteStringToPtr::AddValue(FX_BSTR key, void* value)
 {
     ASSERT(value != NULL);
     _CompactString* pKey = (_CompactString*)m_Buffer.Add();
-    _CompactStringStore(pKey, (FX_LPCBYTE)key, key.GetLength());
+    _CompactStringStore(pKey, key.GetPtr(), key.GetLength());
     *(void**)(pKey + 1) = value;
 }
 void CFX_CMapByteStringToPtr::RemoveKey(FX_BSTR key)
@@ -550,7 +550,7 @@ void CFX_CMapByteStringToPtr::RemoveKey(FX_BSTR key)
     int size = m_Buffer.GetSize();
     for (int index = 0; index < size; index++) {
         _CompactString* pKey = (_CompactString*)m_Buffer.GetAt(index);
-        if (!_CompactStringSame(pKey, (FX_LPCBYTE)key, key_len)) {
+        if (!_CompactStringSame(pKey, key.GetPtr(), key_len)) {
             continue;
         }
         _CompactStringRelease(pKey);
diff --git a/core/src/fxcrt/fx_basic_wstring_unittest.cpp b/core/src/fxcrt/fx_basic_wstring_unittest.cpp
index c6e5c2f3d0..084410ad19 100644
--- a/core/src/fxcrt/fx_basic_wstring_unittest.cpp
+++ b/core/src/fxcrt/fx_basic_wstring_unittest.cpp
@@ -1,29 +1,108 @@
-// 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"

-

-#define ByteStringLiteral(str) CFX_ByteString(FX_BSTRC(str))

-

-TEST(fxcrt, WideStringUTF16LE_Encode) {

-  struct UTF16LEEncodeCase {

-    CFX_WideString ws;

-    CFX_ByteString bs;

-  } utf16le_encode_cases[] = {

-    { L"", ByteStringLiteral("\0\0") },

-    { L"abc", ByteStringLiteral("a\0b\0c\0\0\0") },

-    { L"abcdef", ByteStringLiteral("a\0b\0c\0d\0e\0f\0\0\0") },

-    { L"abc\0def", ByteStringLiteral("a\0b\0c\0\0\0") },

-    { L"\xaabb\xccdd", ByteStringLiteral("\xbb\xaa\xdd\xcc\0\0") },

-    { L"\x3132\x6162", ByteStringLiteral("\x32\x31\x62\x61\0\0") },

-  };

-

-  for (size_t i = 0; i < FX_ArraySize(utf16le_encode_cases); ++i) {

-    EXPECT_EQ(utf16le_encode_cases[i].bs,

-        utf16le_encode_cases[i].ws.UTF16LE_Encode())

-        << " for case number " << i;

-  }

-}

+// 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, WideStringOperatorSubscript) {
+    // CFX_WideString includes the NUL terminator for non-empty strings.
+    CFX_WideString abc(L"abc");
+    EXPECT_EQ(L'a', abc[0]);
+    EXPECT_EQ(L'b', abc[1]);
+    EXPECT_EQ(L'c', abc[2]);
+    EXPECT_EQ(L'\0', abc[3]);
+}
+
+TEST(fxcrt, WideStringOperatorLT) {
+    CFX_WideString empty;
+    CFX_WideString a(L"a");
+    CFX_WideString abc(L"\x0110qq");  // Comes before despite endianness.
+    CFX_WideString def(L"\x1001qq");  // Comes after despite endianness.
+
+    EXPECT_FALSE(empty < empty);
+    EXPECT_FALSE(a < a);
+    EXPECT_FALSE(abc < abc);
+    EXPECT_FALSE(def < def);
+
+    EXPECT_TRUE(empty < a);
+    EXPECT_FALSE(a < empty);
+
+    EXPECT_TRUE(empty < abc);
+    EXPECT_FALSE(abc < empty);
+
+    EXPECT_TRUE(empty < def);
+    EXPECT_FALSE(def < empty);
+
+    EXPECT_TRUE(a < abc);
+    EXPECT_FALSE(abc < a);
+
+    EXPECT_TRUE(a < def);
+    EXPECT_FALSE(def < a);
+
+    EXPECT_TRUE(abc < def);
+    EXPECT_FALSE(def < abc);
+}
+
+#define ByteStringLiteral(str) CFX_ByteString(FX_BSTRC(str))
+
+TEST(fxcrt, WideStringUTF16LE_Encode) {
+  struct UTF16LEEncodeCase {
+    CFX_WideString ws;
+    CFX_ByteString bs;
+  } utf16le_encode_cases[] = {
+    { L"", ByteStringLiteral("\0\0") },
+    { L"abc", ByteStringLiteral("a\0b\0c\0\0\0") },
+    { L"abcdef", ByteStringLiteral("a\0b\0c\0d\0e\0f\0\0\0") },
+    { L"abc\0def", ByteStringLiteral("a\0b\0c\0\0\0") },
+    { L"\xaabb\xccdd", ByteStringLiteral("\xbb\xaa\xdd\xcc\0\0") },
+    { L"\x3132\x6162", ByteStringLiteral("\x32\x31\x62\x61\0\0") },
+  };
+
+  for (size_t i = 0; i < FX_ArraySize(utf16le_encode_cases); ++i) {
+    EXPECT_EQ(utf16le_encode_cases[i].bs,
+        utf16le_encode_cases[i].ws.UTF16LE_Encode())
+        << " for case number " << i;
+  }
+}
+
+TEST(fxcrt, WideStringCOperatorSubscript) {
+    // CFX_WideStringC includes the NUL terminator for non-empty strings.
+    CFX_WideStringC abc(L"abc");
+    EXPECT_EQ(L'a', abc[0]);
+    EXPECT_EQ(L'b', abc[1]);
+    EXPECT_EQ(L'c', abc[2]);
+    EXPECT_EQ(L'\0', abc[3]);
+}
+
+TEST(fxcrt, WideStringCOperatorLT) {
+    CFX_WideStringC empty;
+    CFX_WideStringC a(L"a");
+    CFX_WideStringC abc(L"\x0110qq");  // Comes before despite endianness.
+    CFX_WideStringC def(L"\x1001qq");  // Comes after despite endianness.
+
+    EXPECT_FALSE(empty < empty);
+    EXPECT_FALSE(a < a);
+    EXPECT_FALSE(abc < abc);
+    EXPECT_FALSE(def < def);
+
+    EXPECT_TRUE(empty < a);
+    EXPECT_FALSE(a < empty);
+
+    EXPECT_TRUE(empty < abc);
+    EXPECT_FALSE(abc < empty);
+
+    EXPECT_TRUE(empty < def);
+    EXPECT_FALSE(def < empty);
+
+    EXPECT_TRUE(a < abc);
+    EXPECT_FALSE(abc < a);
+
+    EXPECT_TRUE(a < def);
+    EXPECT_FALSE(def < a);
+
+    EXPECT_TRUE(abc < def);
+    EXPECT_FALSE(def < abc);
+}
+