/**

* @name Equality test on floating-point values

* @description Comparing results of floating-point computations with '==' or

* '!=' is likely to yield surprising results since floating-point

* computation does not follow the standard rules of algebra.

* @kind problem

* @problem.severity recommendation

* @precision high

* @id cpp/equality-on-floats

* @tags reliability

* correctness

*/

import cpp

import semmle.code.cpp.ConfigurationTestFile

from EqualityOperation ro, Expr left, Expr right

where

left = ro.getLeftOperand() and

right = ro.getRightOperand() and

ro.getAnOperand().getExplicitlyConverted().getType().getUnderlyingType() instanceof

FloatingPointType and

not ro.getAnOperand().isConstant() and // comparisons to constants generate too many false positives

not left.(VariableAccess).getTarget() = right.(VariableAccess).getTarget() and // skip self comparison

not ro.getFile() instanceof ConfigurationTestFile // expressions in files generated during configuration are likely false positives

select ro, "Equality checks on floating point values can yield unexpected results."