Merge pull request github#12709 from MathiasVP/disable-rounding-2

C++: Disable floating point rounding in range analysis

Author: MathiasVP

cpp/ql/lib/experimental/semmle/code/cpp/semantic/analysis/FloatDelta.qll

@@ -16,14 +16,5 @@ module FloatDelta implements DeltaSig {
   Delta fromInt(int n) { result = n }
 
   bindingset[f]
-  Delta fromFloat(float f) {
-    result =
-      min(float diff, float res |
-        diff = (res - f) and res = f.ceil()
-        or
-        diff = (f - res) and res = f.floor()
-      |
-        res order by diff
-      )
-  }
+  Delta fromFloat(float f) { result = f }
 }

cpp/ql/test/library-tests/ir/range-analysis/RangeAnalysis.ql

@@ -29,15 +29,15 @@ private string getDirectionString(boolean d) {
 }
 
 bindingset[value]
-private string getOffsetString(int value) {
+private string getOffsetString(float value) {
   if value >= 0 then result = "+" + value.toString() else result = value.toString()
 }
 
 bindingset[s]
 string quote(string s) { if s.matches("% %") then result = "\"" + s + "\"" else result = s }
 
 bindingset[delta]
-private string getBoundString(SemBound b, int delta) {
+private string getBoundString(SemBound b, float delta) {
   b instanceof SemZeroBound and result = delta.toString()
   or
   result =
@@ -51,7 +51,7 @@ private string getBoundString(SemBound b, int delta) {
 }
 
 private string getARangeString(SemExpr e) {
-  exists(SemBound b, int delta, boolean upper |
+  exists(SemBound b, float delta, boolean upper |
     semBounded(e, b, delta, upper, _) and
     if semBounded(e, b, delta, upper.booleanNot(), _)
     then delta != 0 and result = "==" + getBoundString(b, delta)

cpp/ql/test/library-tests/ir/range-analysis/SimpleRangeAnalysis_tests.cpp

@@ -741,7 +741,7 @@ unsigned long mult_rounding() {
   range(y); // $ range===1000000003
   range(x); // $ range===1000000003
   xy = x * y;
-  range(xy); // $ range===2147483647
+  range(xy); // $ range===1000000006000000000
   return xy; // BUG: upper bound should be >= 1000000006000000009UL
 }