Merge pull request github#5543 from MathiasVP/smart-ptr-like-class

C++: Add a class that models wrapped pointer types

Author: Dave Bartolomeo

cpp/ql/src/semmle/code/cpp/exprs/Call.qll

@@ -300,6 +300,14 @@ class FunctionCall extends Call, @funbindexpr {
   }
 }
 
+/** A _user-defined_ unary `operator*` function. */
+class OverloadedPointerDereferenceFunction extends Function {
+  OverloadedPointerDereferenceFunction() {
+    this.hasName("operator*") and
+    this.getEffectiveNumberOfParameters() = 1
+  }
+}
+
 /**
  * An instance of a _user-defined_ unary `operator*` applied to its argument.
  * ```
@@ -309,8 +317,7 @@ class FunctionCall extends Call, @funbindexpr {
  */
 class OverloadedPointerDereferenceExpr extends FunctionCall {
   OverloadedPointerDereferenceExpr() {
-    getTarget().hasName("operator*") and
-    getTarget().getEffectiveNumberOfParameters() = 1
+    this.getTarget() instanceof OverloadedPointerDereferenceFunction
   }
 
   override string getAPrimaryQlClass() { result = "OverloadedPointerDereferenceExpr" }

cpp/ql/src/semmle/code/cpp/models/implementations/SmartPointer.qll

@@ -1,10 +1,17 @@
 import semmle.code.cpp.models.interfaces.Taint
+import semmle.code.cpp.models.interfaces.PointerWrapper
 
 /**
  * The `std::shared_ptr` and `std::unique_ptr` template classes.
  */
-private class UniqueOrSharedPtr extends Class {
+private class UniqueOrSharedPtr extends Class, PointerWrapper {
   UniqueOrSharedPtr() { this.hasQualifiedName(["std", "bsl"], ["shared_ptr", "unique_ptr"]) }
+
+  override MemberFunction getAnUnwrapperFunction() {
+    result.(OverloadedPointerDereferenceFunction).getDeclaringType() = this
+    or
+    result.getClassAndName(["operator->", "get"]) = this
+  }
 }
 
 /**

cpp/ql/src/semmle/code/cpp/models/interfaces/PointerWrapper.qll

@@ -0,0 +1,14 @@
+/** Provides classes for modeling pointer wrapper types and expressions. */
+
+private import cpp
+
+/** A class that wraps a pointer type. For example, `std::unique_ptr` and `std::shared_ptr`. */
+abstract class PointerWrapper extends Class {
+  /**
+   * Gets a member function of this class that returns the wrapped pointer, if any.
+   *
+   * This includes both functions that return the wrapped pointer by value, and functions
+   * that return a reference to the pointed-to object.
+   */
+  abstract MemberFunction getAnUnwrapperFunction();
+}