C++: Filter out lower bounds on overflowing exprs

Robert Marsh · Robert Marsh · commit 0cd6941a21f6 · 2020-11-24T12:57:11.000-08:00
Fixes performance issues where multiple lower bounds would be
computed for overflowing expressions
diff --git a/cpp/ql/src/semmle/code/cpp/rangeanalysis/SimpleRangeAnalysis.qll b/cpp/ql/src/semmle/code/cpp/rangeanalysis/SimpleRangeAnalysis.qll
@@ -625,7 +625,8 @@ private float getTruncatedLowerBounds(Expr expr) {
               )
           else result = newLB
         else result = exprMinVal(expr)
-      )
+      ) and
+      getUpperBoundsImpl(expr) <= exprMaxVal(expr)
       or
       // The expression might overflow and wrap. If so, the
       // lower bound is exprMinVal.
