QString::toStdString() doesn't call new operator but delete operator is called on destruction with invalid pointer

I have a large application that implements global overloaded new/delete operators.  When I debug and place breakpoints at the overloaded new and delete operators and try this code (with QString qsFilter)

const std::string fs = qsFilter.toStdString(); 

OR this code

      const QByteArray ba( qsFilter.toLocal8Bit() );

      const std::string fs = ba.toStdString();

it doesn't hit the breakpoint at my overloaded new operator, however when the object comes out of scope and is destroyed, it hits the breakpoint at my overloaded delete operator with a bad pointer and the application crashes when it attempts to free memory using this invalid pointer.

On the other hand, this code behaves as expected and it hits both breakpoints:

   {
      const QByteArray ba( qsFilter.toLocal8Bit() );     
       const std::string fs = ba.constData(); 
   }

NOTE: I used Dependency Walker to make sure that I wasn't linking to new/delete operators in some other library, so I know that this is not the issue.  This only seems to happen with toStdString() and also with toStdWString().  The application program runs fine without any other issues that I would expect if this was the case.

I ended up going through the code in the application program and replacing (for now) code that was calling toStdString() with qPrintable(..) or the equivalent QByteArray based code that I know works well.