Bug 504660 Make sEmptyBuffer non-const so EnsureMutable can safely use it for an empty string r=bsmedberg

xpcom/string/public/nsCharTraits.h

@@ -151,7 +151,7 @@ struct nsCharTraits<PRUnichar>
     typedef PRUint16  unsigned_char_type;
     typedef char      incompatible_char_type;
 
-    NS_COM static const char_type *sEmptyBuffer;
+    NS_COM static char_type *sEmptyBuffer;
 
     static
     void
@@ -441,7 +441,7 @@ struct nsCharTraits<char>
     typedef unsigned char  unsigned_char_type;
     typedef PRUnichar      incompatible_char_type;
 
-    NS_COM static const char_type *sEmptyBuffer;
+    NS_COM static char_type *sEmptyBuffer;
 
     static
     void

xpcom/string/public/nsTString.h

@@ -560,11 +560,11 @@ class nsTXPIDLString_CharT : public nsTString_CharT
     public:
 
       nsTXPIDLString_CharT()
-        : string_type(const_cast<char_type*>(char_traits::sEmptyBuffer), 0, F_TERMINATED | F_VOIDED) {}
+        : string_type(char_traits::sEmptyBuffer, 0, F_TERMINATED | F_VOIDED) {}
 
         // copy-constructor required to avoid default
       nsTXPIDLString_CharT( const self_type& str )
-        : string_type(const_cast<char_type*>(char_traits::sEmptyBuffer), 0, F_TERMINATED | F_VOIDED)
+        : string_type(char_traits::sEmptyBuffer, 0, F_TERMINATED | F_VOIDED)
         {
           Assign(str);
         }

xpcom/string/src/nsSubstring.cpp

@@ -54,10 +54,10 @@
 
 // ---------------------------------------------------------------------------
 
-static const PRUnichar gNullChar = 0;
+static PRUnichar gNullChar = 0;
 
-const char*      nsCharTraits<char>     ::sEmptyBuffer = (const char*) &gNullChar;
-const PRUnichar* nsCharTraits<PRUnichar>::sEmptyBuffer =               &gNullChar;
+char*      nsCharTraits<char>     ::sEmptyBuffer = (char*) &gNullChar;
+PRUnichar* nsCharTraits<PRUnichar>::sEmptyBuffer =         &gNullChar;
 
 // ---------------------------------------------------------------------------
 

xpcom/string/src/nsTSubstring.cpp

@@ -59,7 +59,7 @@ nsTSubstring_CharT::nsTSubstring_CharT(const substring_tuple_type& tuple)
 }
 
 nsTSubstring_CharT::nsTSubstring_CharT()
-: mData(const_cast<char_type*>(char_traits::sEmptyBuffer)),
+: mData(char_traits::sEmptyBuffer),
   mLength(0),
   mFlags(F_TERMINATED) {}
 
@@ -563,7 +563,7 @@ nsTSubstring_CharT::SetCapacity( size_type capacity )
     if (capacity == 0)
       {
         ::ReleaseData(mData, mFlags);
-        mData = const_cast<char_type*>(char_traits::sEmptyBuffer);
+        mData = char_traits::sEmptyBuffer;
         mLength = 0;
         SetDataFlags(F_TERMINATED);
       }