don't call CopyBeforeWrite when returning non-const interator if the string is empty -- avoids assert and is not needed anyway since the iterator is never valid

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@27539 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/string.h

@@ -429,9 +429,9 @@ public:
   const_iterator end() const { return m_pchData + length(); }
 
   // first valid index position
-  iterator begin() { CopyBeforeWrite(); return m_pchData; }
+  iterator begin();
   // position one after the last valid one
-  iterator end() { CopyBeforeWrite(); return m_pchData + length(); }
+  iterator end();
 
     // insert another string
   wxStringBase& insert(size_t nPos, const wxStringBase& str)

src/common/string.cpp

@@ -408,6 +408,20 @@ bool wxStringBase::Alloc(size_t nLen)
   return TRUE;
 }
   
+wxStringBase::iterator wxStringBase::begin()
+{
+    if (length() > 0)
+        CopyBeforeWrite();
+    return m_pchData;
+}
+
+wxStringBase::iterator wxStringBase::end()
+{
+    if (length() > 0)
+        CopyBeforeWrite();
+    return m_pchData + length();
+}
+
 wxStringBase::iterator wxStringBase::erase(iterator it)
 {
     size_type idx = it - begin();