C++: Add a SimpleRangeAnalysisDefinition test def

Author: jbj

cpp/ql/test/experimental/library-tests/rangeanalysis/extensibility/extensibility.expected

@@ -5,5 +5,5 @@
 | extensibility.c:12:16:12:16 | x | -2.147483648E9 | 2.147483647E9 |
 | extensibility.c:12:20:12:20 | x | -2.147483648E9 | 2.147483647E9 |
 | extensibility.c:13:10:13:15 | result | 0.0 | 0.0 |
-| extensibility.c:17:3:17:23 | magic_name_at_most_10 | -2.147483648E9 | 2.147483647E9 |
-| extensibility.c:18:3:18:23 | magic_name_at_most_20 | -2.147483648E9 | 2.147483647E9 |
+| extensibility.c:17:3:17:23 | magic_name_at_most_10 | -2.147483648E9 | 10.0 |
+| extensibility.c:18:3:18:23 | magic_name_at_most_20 | -2.147483648E9 | 20.0 |

cpp/ql/test/experimental/library-tests/rangeanalysis/extensibility/extensibility.ql

@@ -1,5 +1,7 @@
 import semmle.code.cpp.rangeanalysis.SimpleRangeAnalysis
+import semmle.code.cpp.rangeanalysis.RangeAnalysisUtils // for typeLowerBound
 import experimental.semmle.code.cpp.models.interfaces.SimpleRangeAnalysisExpr
+import experimental.semmle.code.cpp.models.interfaces.SimpleRangeAnalysisDefinition
 
 class CustomAddFunctionCall extends SimpleRangeAnalysisExpr, FunctionCall {
   CustomAddFunctionCall() { this.getTarget().hasGlobalName("custom_add_function") }
@@ -37,6 +39,40 @@ class SelfSub extends SimpleRangeAnalysisExpr, SubExpr {
   override predicate dependsOnChild(Expr child) { child = this.getAnOperand() }
 }
 
+/**
+ * A definition for test purposes of a parameter `p` that starts with a
+ * special prefix. This class is written to exploit how QL behaves when class
+ * fields are not functionally determined by `this`. When multiple parameters
+ * of the same function have the special prefix, there is still only one
+ * instance of this class.
+ */
+class MagicParameterName extends SimpleRangeAnalysisDefinition {
+  Parameter p;
+  float value;
+
+  MagicParameterName() {
+    this.definedByParameter(p) and
+    value = p.getName().regexpCapture("magic_name_at_most_(\\d+)", 1).toFloat()
+  }
+
+  override predicate hasRangeInformationFor(StackVariable v) { v = p }
+
+  override predicate dependsOnExpr(StackVariable v, Expr e) {
+    // No dependencies. This sample class yields constant values.
+    none()
+  }
+
+  override float getLowerBounds(StackVariable var) {
+    var = p and
+    result = typeLowerBound(p.getUnspecifiedType())
+  }
+
+  override float getUpperBounds(StackVariable var) {
+    var = p and
+    result = value
+  }
+}
+
 from VariableAccess expr, float lower, float upper
 where
   lower = lowerBound(expr) and