PVS-Studio warning V547 for TPP

int Dta2mzXML::extractScanNum(const string& dtaFileName)
{
  ...
  std::string::size_type pos = dtaFileName.rfind("/");

  if (pos < 0)  {
    pos = dtaFileName.rfind("\\");
  }
  ...
}

This is what should have been written here: (pos == string::npos).


This suspicious code was found in TPP project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'pos < 0' is always false. Unsigned type value is never < 0. dta2mzXML dta2mzxml.cpp 622

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