Avoid integer divide by zero

[kevinbackhouse]

The main change here is to fix an integer divide by zero in src/minoltamn_int.cpp.

I also added some defensive coding to avoid the FPE that could be caused by 0x80000000/0xFFFFFFFF: rather than checking that the denominator is not zero, check that the denominator is greater than zero. I doubt that we are ever deliberately using negative denominators, so I think it should be a safe change.

[kevinbackhouse]

This is the CodeQL query that I used to search for integer divide operations:

import cpp
import semmle.code.cpp.rangeanalysis.SimpleRangeAnalysis

from DivExpr div, Expr rhs
where
  rhs = div.getRightOperand() and
  div.getType() instanceof IntegralType and
  not (lowerBound(rhs) > 0 or upperBound(rhs) < 0) and
  not rhs instanceof SizeofOperator and
  exists(rhs.getLocation().getFile().getRelativePath())
select rhs, rhs.getType()

[hassec]

👍 great stuff!