catching 32/64 bit integer mixing

[Drew Parsons <dparsons@debian.org>]

An upstream author has asked whether we know of tools or compiler flags 
to help catch problems mixing 64 and 32 bit integers, for instance 
catching implicit conversions, as in

  int64_t n = ...;
  for (int32_t i=0; i<n; i++) {
    ...
  }

There is -fsanitize=signed-integer-overflow (which generates a runtime 
error message), but that requires data to cause overflow at every 
possible location.

Is there a better tool for catching this kind of problem?

Drew