PVS-Studio warning V567 for CryEngineSDK

void AddSample( T x )
{
  m_index = ++m_index % N;
  ....
}

This suspicious code was found in CryEngineSDK project by PVS-Studio static code analyzer.
Warning message is:
V567 Undefined behavior. The 'm_index' variable is modified while being used twice between sequence points. inetwork.h 2303

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