Looking for unsigned comparison warning

[mathieu]

Hello,

  I am looking for a flag that would warn me about someting like this
(*). I have tried so far:

$ g++ -Wall -Wextra -Wconversion -Wsign-compare -g unsigned.cxx

Thanks
-Mathieu
(*)
#include <iostream>

unsigned int size()
{
  return 0;
}

int main(int, char*[])
{
  unsigned int s = size();
  unsigned int index = 1;
  if ( index <= s - 1 )
    {
    std::cout << index << " is valid for size " << s << std::endl;
    }
  return 0;
}