Q: Is there a good way to overcome this apparent bug without modifying the
mfc code?
___________________________________

Info:  Although it is NOT a good idea, I seemed to have perhaps located a
bug in this function with the GetLength call whose results are sent to the
sub-call to Concatenate.  So I added the following and it asserts on
particular strings that are used.  (I am not sure if this makes any
difference, but I am using class derived from CString that ends up calling
this code...  However, that class never does anything remotely like touching
any private CString data without going through  the very normal exposed
methods.)

Code as modified in CStringT.h file (line# 2013):
friend CStringT operator+( const CStringT& str1, const CStringT& str2 )
{
 CStringT strResult( str1.GetManager() );
   
 int str1_GetLength = str1.GetLength();
 int str1_lstrlen   = lstrlen(str1);
 int str2_GetLength = str2.GetLength();
 int str2_lstrlen   = lstrlen(str2);
 ASSERT ( str1_GetLength == str1_lstrlen );
 ASSERT ( str2_GetLength == str2_lstrlen );

 Concatenate( strResult, str1, str1.GetLength(), str2, str2.GetLength() );

 return( strResult );
}
______________________________
Values are as follows as the debugger is about to eexecute the first ASSERT
statement:

str1 {0x0127a658 "<Message>"}    const
ATL::CStringT<char,StrTraitMFC_DLL<char,ATL::ChTraitsCRT<char> > > &

str2 {0x0127a4a8 "chris logged off."}const
ATL::CStringT<char,StrTraitMFC_DLL<char,ATL::ChTraitsCRT<char> > > &

str1_GetLength  9  int

str1_lstrlen  9  int

str2_GetLength  18  int

str2_lstrlen  17  int

Ignore the assert and the result is:
strResult  {0x0127a5a8 "<Message>chris logged off."}
ATL::CStringT<char,StrTraitMFC_DLL<char,ATL::ChTraitsCRT<char> > >

________________________________

Notice that in this instance, the second assert will fail.  If I ignore it,
then then next time I enter this function on this string to concatenate more,
the str1 length is wrong and the concantenation writes the added string just
after the null so that the result is incorrect.

___________________________________

str1_GetLength  27  int

str1_lstrlen  26  int

str2_GetLength  2  int

str2_lstrlen  2  int

str1  {0x0127a5a8 "<Message>chris logged off."}  const
ATL::CStringT<char,StrTraitMFC_DLL<char,ATL::ChTraitsCRT<char> > > &

str2  {0x0127a610 "</"}  const
ATL::CStringT<char,StrTraitMFC_DLL<char,ATL::ChTraitsCRT<char> > > &

strResult {0x012525b8 "<Message>chris logged off."}
ATL::CStringT<char,StrTraitMFC_DLL<char,ATL::ChTraitsCRT<char> > >
_____________________________

Tony_Morris at Teledyne dot com