Merge pull request #5607 from MathiasVP/smart-pointer-ast-read-store-steps

C++: read and store steps for smart pointers in AST dataflow

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

@@ -1,4 +1,5 @@
 import semmle.code.cpp.models.interfaces.Taint
+import semmle.code.cpp.models.interfaces.DataFlow
 import semmle.code.cpp.models.interfaces.PointerWrapper
 
 /**
@@ -14,6 +15,23 @@ private class UniqueOrSharedPtr extends Class, PointerWrapper {
   }
 }
 
+/** Any function that unwraps a pointer wrapper class to reveal the underlying pointer. */
+private class PointerWrapperDataFlow extends DataFlowFunction {
+  PointerWrapperDataFlow() {
+    this = any(PointerWrapper wrapper).getAnUnwrapperFunction() and
+    not this.getUnspecifiedType() instanceof ReferenceType
+  }
+
+  override predicate hasDataFlow(FunctionInput input, FunctionOutput output) {
+    input.isQualifierAddress() and output.isReturnValue()
+    or
+    input.isQualifierObject() and output.isReturnValueDeref()
+    or
+    input.isReturnValueDeref() and
+    output.isQualifierObject()
+  }
+}
+
 /**
  * The `std::make_shared` and `std::make_unique` template functions.
  */