C++: Support default arguments in constructors and accept test changes.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll

@@ -603,15 +603,15 @@ private Type stripReferences(Type unspecifiedType) {
 private predicate forwardingCallTargetsConstructor(
   CallInstruction call, Cpp::Constructor constructor
 ) {
-  exists(int start |
+  exists(int start, int numberOfForwardedArguments |
     External::forwards(call.getStaticCallTarget(), constructor, start) and
-    call.getNumberOfPositionalArguments() = start + constructor.getNumberOfParameters() and
-    forall(int i, Type typeCall, Type typeConstructor |
-      i = [0 .. constructor.getNumberOfParameters() - 1] and
-      typeCall = stripReferences(call.getPositionalArgument(start + i).getResultType()) and
-      typeConstructor = stripReferences(constructor.getParameter(i).getUnspecifiedType())
-    |
-      typeCall = typeConstructor
+    call.getNumberOfPositionalArguments() = start + numberOfForwardedArguments and
+    forall(int i | i = [0 .. constructor.getNumberOfParameters() - 1] |
+      i < numberOfForwardedArguments and
+      stripReferences(call.getPositionalArgument(start + i).getResultType()) =
+        stripReferences(constructor.getParameter(i).getUnspecifiedType())
+      or
+      i >= numberOfForwardedArguments and constructor.getParameter(i).hasInitializer()
     )
   )
 }

cpp/ql/test/library-tests/dataflow/external-models/flow.expected

@@ -392,6 +392,15 @@ edges
 | test.cpp:397:20:397:22 | call to get [x] | test.cpp:398:11:398:11 | *e [x] | provenance |  |
 | test.cpp:398:11:398:11 | *e [x] | test.cpp:398:13:398:13 | x | provenance |  |
 | test.cpp:398:13:398:13 | x | test.cpp:398:13:398:13 | x | provenance | Sink:MaD:3 |
+| test.cpp:408:11:408:19 | call to ymlSource | test.cpp:408:11:408:19 | call to ymlSource | provenance | Src:MaD:48  |
+| test.cpp:408:11:408:19 | call to ymlSource | test.cpp:409:16:409:16 | *x | provenance |  |
+| test.cpp:409:3:409:3 | emplace output argument [element, x] | test.cpp:411:34:411:34 | *c [element, x] | provenance |  |
+| test.cpp:409:16:409:16 | *x | test.cpp:409:3:409:3 | emplace output argument [element, x] | provenance | MaD:87 |
+| test.cpp:411:34:411:34 | *c [element, x] | test.cpp:411:39:411:41 | call to get [x] | provenance | MaD:88 |
+| test.cpp:411:39:411:41 | call to get [x] | test.cpp:411:39:411:41 | call to get [x] | provenance |  |
+| test.cpp:411:39:411:41 | call to get [x] | test.cpp:412:11:412:11 | *e [x] | provenance |  |
+| test.cpp:412:11:412:11 | *e [x] | test.cpp:412:13:412:13 | x | provenance |  |
+| test.cpp:412:13:412:13 | x | test.cpp:412:13:412:13 | x | provenance | Sink:MaD:3 |
 | windows.cpp:22:15:22:29 | *call to GetCommandLineA | windows.cpp:24:8:24:11 | * ... | provenance |  |
 | windows.cpp:22:15:22:29 | *call to GetCommandLineA | windows.cpp:27:36:27:38 | *cmd | provenance |  |
 | windows.cpp:22:15:22:29 | call to GetCommandLineA | windows.cpp:22:15:22:29 | *call to GetCommandLineA | provenance | Src:MaD:5  |
@@ -890,6 +899,16 @@ nodes
 | test.cpp:398:11:398:11 | *e [x] | semmle.label | *e [x] |
 | test.cpp:398:13:398:13 | x | semmle.label | x |
 | test.cpp:398:13:398:13 | x | semmle.label | x |
+| test.cpp:408:11:408:19 | call to ymlSource | semmle.label | call to ymlSource |
+| test.cpp:408:11:408:19 | call to ymlSource | semmle.label | call to ymlSource |
+| test.cpp:409:3:409:3 | emplace output argument [element, x] | semmle.label | emplace output argument [element, x] |
+| test.cpp:409:16:409:16 | *x | semmle.label | *x |
+| test.cpp:411:34:411:34 | *c [element, x] | semmle.label | *c [element, x] |
+| test.cpp:411:39:411:41 | call to get [x] | semmle.label | call to get [x] |
+| test.cpp:411:39:411:41 | call to get [x] | semmle.label | call to get [x] |
+| test.cpp:412:11:412:11 | *e [x] | semmle.label | *e [x] |
+| test.cpp:412:13:412:13 | x | semmle.label | x |
+| test.cpp:412:13:412:13 | x | semmle.label | x |
 | windows.cpp:22:15:22:29 | *call to GetCommandLineA | semmle.label | *call to GetCommandLineA |
 | windows.cpp:22:15:22:29 | call to GetCommandLineA | semmle.label | call to GetCommandLineA |
 | windows.cpp:24:8:24:11 | * ... | semmle.label | * ... |

cpp/ql/test/library-tests/dataflow/external-models/test.cpp

@@ -409,5 +409,5 @@ void forward_test_model_with_default_argument() {
   c.emplace(0, x);
 
   ElementWithDefaultArgument e = c.get();
-  ymlSink(e.x); // $ MISSING: ir
+  ymlSink(e.x); // $ ir
 }