diff --git a/core/fpdfdoc/cpvt_wordinfo.cpp b/core/fpdfdoc/cpvt_wordinfo.cpp
index 7712bcd..1e1556b 100644
--- a/core/fpdfdoc/cpvt_wordinfo.cpp
+++ b/core/fpdfdoc/cpvt_wordinfo.cpp
@@ -36,9 +36,9 @@
 
 CPVT_WordInfo::~CPVT_WordInfo() {}
 
-void CPVT_WordInfo::operator=(const CPVT_WordInfo& word) {
+CPVT_WordInfo& CPVT_WordInfo::operator=(const CPVT_WordInfo& word) {
   if (this == &word)
-    return;
+    return *this;
 
   Word = word.Word;
   nCharset = word.nCharset;
@@ -46,4 +46,5 @@
   fWordX = word.fWordX;
   fWordY = word.fWordY;
   fWordTail = word.fWordTail;
+  return *this;
 }
diff --git a/core/fpdfdoc/cpvt_wordinfo.h b/core/fpdfdoc/cpvt_wordinfo.h
index 401b9a5..e23ab2c 100644
--- a/core/fpdfdoc/cpvt_wordinfo.h
+++ b/core/fpdfdoc/cpvt_wordinfo.h
@@ -15,7 +15,7 @@
   CPVT_WordInfo(const CPVT_WordInfo& word);
   ~CPVT_WordInfo();
 
-  void operator=(const CPVT_WordInfo& word);
+  CPVT_WordInfo& operator=(const CPVT_WordInfo& word);
 
   uint16_t Word;
   int32_t nCharset;
diff --git a/core/fxcrt/bytestring.cpp b/core/fxcrt/bytestring.cpp
index 824ec85..a38dc15 100644
--- a/core/fxcrt/bytestring.cpp
+++ b/core/fxcrt/bytestring.cpp
@@ -189,58 +189,58 @@
 
 ByteString::~ByteString() {}
 
-const ByteString& ByteString::operator=(const char* pStr) {
-  if (!pStr || !pStr[0])
+ByteString& ByteString::operator=(const char* str) {
+  if (!str || !str[0])
     clear();
   else
-    AssignCopy(pStr, strlen(pStr));
+    AssignCopy(str, strlen(str));
 
   return *this;
 }
 
-const ByteString& ByteString::operator=(ByteStringView bstrc) {
-  if (bstrc.IsEmpty())
+ByteString& ByteString::operator=(ByteStringView str) {
+  if (str.IsEmpty())
     clear();
   else
-    AssignCopy(bstrc.unterminated_c_str(), bstrc.GetLength());
+    AssignCopy(str.unterminated_c_str(), str.GetLength());
 
   return *this;
 }
 
-const ByteString& ByteString::operator=(const ByteString& that) {
+ByteString& ByteString::operator=(const ByteString& that) {
   if (m_pData != that.m_pData)
     m_pData = that.m_pData;
 
   return *this;
 }
 
-const ByteString& ByteString::operator=(ByteString&& that) {
+ByteString& ByteString::operator=(ByteString&& that) {
   if (m_pData != that.m_pData)
     m_pData = std::move(that.m_pData);
 
   return *this;
 }
 
-const ByteString& ByteString::operator+=(const char* pStr) {
-  if (pStr)
-    Concat(pStr, strlen(pStr));
+ByteString& ByteString::operator+=(const char* str) {
+  if (str)
+    Concat(str, strlen(str));
 
   return *this;
 }
 
-const ByteString& ByteString::operator+=(char ch) {
+ByteString& ByteString::operator+=(char ch) {
   Concat(&ch, 1);
   return *this;
 }
 
-const ByteString& ByteString::operator+=(const ByteString& str) {
+ByteString& ByteString::operator+=(const ByteString& str) {
   if (str.m_pData)
     Concat(str.m_pData->m_String, str.m_pData->m_nDataLength);
 
   return *this;
 }
 
-const ByteString& ByteString::operator+=(ByteStringView str) {
+ByteString& ByteString::operator+=(ByteStringView str) {
   if (!str.IsEmpty())
     Concat(str.unterminated_c_str(), str.GetLength());
 
diff --git a/core/fxcrt/bytestring.h b/core/fxcrt/bytestring.h
index 72d629a..d525050 100644
--- a/core/fxcrt/bytestring.h
+++ b/core/fxcrt/bytestring.h
@@ -131,15 +131,15 @@
   bool operator<(ByteStringView str) const;
   bool operator<(const ByteString& other) const;
 
-  const ByteString& operator=(const char* str);
-  const ByteString& operator=(ByteStringView bstrc);
-  const ByteString& operator=(const ByteString& that);
-  const ByteString& operator=(ByteString&& that);
+  ByteString& operator=(const char* str);
+  ByteString& operator=(ByteStringView str);
+  ByteString& operator=(const ByteString& that);
+  ByteString& operator=(ByteString&& that);
 
-  const ByteString& operator+=(char ch);
-  const ByteString& operator+=(const char* str);
-  const ByteString& operator+=(const ByteString& str);
-  const ByteString& operator+=(ByteStringView str);
+  ByteString& operator+=(char ch);
+  ByteString& operator+=(const char* str);
+  ByteString& operator+=(const ByteString& str);
+  ByteString& operator+=(ByteStringView str);
 
   CharType operator[](const size_t index) const {
     CHECK(IsValidIndex(index));
diff --git a/core/fxcrt/fx_coordinates.h b/core/fxcrt/fx_coordinates.h
index a071693..5bb36da 100644
--- a/core/fxcrt/fx_coordinates.h
+++ b/core/fxcrt/fx_coordinates.h
@@ -24,7 +24,7 @@
   CFX_PTemplate(BaseType new_x, BaseType new_y) : x(new_x), y(new_y) {}
   CFX_PTemplate(const CFX_PTemplate& other) : x(other.x), y(other.y) {}
 
-  CFX_PTemplate operator=(const CFX_PTemplate& other) {
+  CFX_PTemplate& operator=(const CFX_PTemplate& other) {
     if (this != &other) {
       x = other.x;
       y = other.y;
@@ -81,7 +81,7 @@
     width = 0;
     height = 0;
   }
-  CFX_STemplate operator=(const CFX_STemplate& other) {
+  CFX_STemplate& operator=(const CFX_STemplate& other) {
     if (this != &other) {
       width = other.width;
       height = other.height;
diff --git a/core/fxcrt/widestring.cpp b/core/fxcrt/widestring.cpp
index a00ce2d..2340b14 100644
--- a/core/fxcrt/widestring.cpp
+++ b/core/fxcrt/widestring.cpp
@@ -385,58 +385,58 @@
 
 WideString::~WideString() {}
 
-const WideString& WideString::operator=(const wchar_t* pStr) {
-  if (!pStr || !pStr[0])
+WideString& WideString::operator=(const wchar_t* str) {
+  if (!str || !str[0])
     clear();
   else
-    AssignCopy(pStr, wcslen(pStr));
+    AssignCopy(str, wcslen(str));
 
   return *this;
 }
 
-const WideString& WideString::operator=(WideStringView stringSrc) {
-  if (stringSrc.IsEmpty())
+WideString& WideString::operator=(WideStringView str) {
+  if (str.IsEmpty())
     clear();
   else
-    AssignCopy(stringSrc.unterminated_c_str(), stringSrc.GetLength());
+    AssignCopy(str.unterminated_c_str(), str.GetLength());
 
   return *this;
 }
 
-const WideString& WideString::operator=(const WideString& that) {
+WideString& WideString::operator=(const WideString& that) {
   if (m_pData != that.m_pData)
     m_pData = that.m_pData;
 
   return *this;
 }
 
-const WideString& WideString::operator=(WideString&& that) {
+WideString& WideString::operator=(WideString&& that) {
   if (m_pData != that.m_pData)
     m_pData = std::move(that.m_pData);
 
   return *this;
 }
 
-const WideString& WideString::operator+=(const wchar_t* pStr) {
-  if (pStr)
-    Concat(pStr, wcslen(pStr));
+WideString& WideString::operator+=(const wchar_t* str) {
+  if (str)
+    Concat(str, wcslen(str));
 
   return *this;
 }
 
-const WideString& WideString::operator+=(wchar_t ch) {
+WideString& WideString::operator+=(wchar_t ch) {
   Concat(&ch, 1);
   return *this;
 }
 
-const WideString& WideString::operator+=(const WideString& str) {
+WideString& WideString::operator+=(const WideString& str) {
   if (str.m_pData)
     Concat(str.m_pData->m_String, str.m_pData->m_nDataLength);
 
   return *this;
 }
 
-const WideString& WideString::operator+=(WideStringView str) {
+WideString& WideString::operator+=(WideStringView str) {
   if (!str.IsEmpty())
     Concat(str.unterminated_c_str(), str.GetLength());
 
diff --git a/core/fxcrt/widestring.h b/core/fxcrt/widestring.h
index ec121ba..96bb3c4 100644
--- a/core/fxcrt/widestring.h
+++ b/core/fxcrt/widestring.h
@@ -111,15 +111,15 @@
   bool IsValidIndex(size_t index) const { return index < GetLength(); }
   bool IsValidLength(size_t length) const { return length <= GetLength(); }
 
-  const WideString& operator=(const wchar_t* str);
-  const WideString& operator=(WideStringView stringSrc);
-  const WideString& operator=(const WideString& that);
-  const WideString& operator=(WideString&& that);
+  WideString& operator=(const wchar_t* str);
+  WideString& operator=(WideStringView str);
+  WideString& operator=(const WideString& that);
+  WideString& operator=(WideString&& that);
 
-  const WideString& operator+=(const wchar_t* str);
-  const WideString& operator+=(wchar_t ch);
-  const WideString& operator+=(const WideString& str);
-  const WideString& operator+=(WideStringView str);
+  WideString& operator+=(const wchar_t* str);
+  WideString& operator+=(wchar_t ch);
+  WideString& operator+=(const WideString& str);
+  WideString& operator+=(WideStringView str);
 
   bool operator==(const wchar_t* ptr) const;
   bool operator==(WideStringView str) const;