PVS-Studio warning V567 for VirtualBox

template<class C> class ConsoleEventBuffer
{
public:
  ....
  C get()
  {
    C c;
    if (full || curg != curp)
    {
      c = buf[curg];
      ++curg %= sz;             //<==
      full = false;
    }
    return c;
  }
....
};

This suspicious code was found in VirtualBox project by PVS-Studio static code analyzer.
Warning message is:
V567 Undefined behavior. The 'curg' variable is modified while being used twice between sequence points. consoleevents.h 75

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/