C++: Add a new test to test assignment certainty (i.e., whether the entire buffer is overwritten).

cpp/ql/test/library-tests/dataflow/certain/test.cpp

@@ -0,0 +1,64 @@
+void use(...);
+
+void test1() {
+  int x = 0; // $ certain="SSA def(&x)" certain="SSA def(x)"
+  use(x);
+
+  x = 1; // $ certain="SSA def(x)"
+  use(x);
+
+  int* p = &x; // $ certain="SSA def(&p)" certain="SSA def(p)" certain="SSA def(*p)"
+  use(p);
+
+  *p = 2; // $ certain="SSA def(*p)"
+  use(p);
+
+  p = nullptr; // $ certain="SSA def(p)" certain="SSA def(*p)"
+  use(p);
+
+  *p = 2; // $ uncertain="SSA def(*p)"
+  use(p);
+}
+
+void test2(bool b) { // $ certain="SSA def(&b)" certain="SSA def(b)"
+  {
+  int x; // $ certain="SSA def(&x)" 
+  if(b) {
+    x = 0; // $ certain="SSA def(x)"
+  } else {
+    x = 1; // $ certain="SSA def(x)"
+  }
+  use(x); // $ uncertain="SSA phi(x)"
+  }
+
+  {
+  int x; // $ certain="SSA def(&x)" certain="SSA def(x)"
+  if(b) {
+    x = 0; // $ certain="SSA def(x)"
+  } else {
+  
+  }
+  use(x); // $ uncertain="SSA phi(x)"
+  }
+
+  {
+  int x; // $ certain="SSA def(&x)" certain="SSA def(x)"
+  int* p = &x; // $ certain="SSA def(&p)" certain="SSA def(p)" certain="SSA def(*p)"
+  if(b) {
+    *p = 0; // $ certain="SSA def(*p)"
+  } else {
+    *(p + 1) = 1; // $ uncertain="SSA def(*p)"
+  }
+  use(p); // $ uncertain="SSA phi(*p)"
+  }
+  
+}
+
+void test3(bool b) { // $ certain="SSA def(&b)" certain="SSA def(b)"
+  for(int i = 0; i < 10;) { // $ certain="SSA def(&i)" certain="SSA def(i)" uncertain="SSA phi(i)"
+    if(b) {
+      ++i; // $ certain="SSA def(i)"
+    }
+    use(i); // $ uncertain="SSA phi(i)"
+  }
+}

cpp/ql/test/library-tests/dataflow/certain/test.ql

@@ -0,0 +1,22 @@
+import cpp
+import utils.test.InlineExpectationsTest
+import semmle.code.cpp.dataflow.new.DataFlow::DataFlow
+
+bindingset[s]
+string quote(string s) { if s.matches("% %") then result = "\"" + s + "\"" else result = s }
+
+module AsDefinitionTest implements TestSig {
+  string getARelevantTag() { result = ["certain", "uncertain"] }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(Ssa::Definition d |
+      location = d.getLocation() and
+      element = d.toString() and
+      value = quote(d.toString())
+    |
+      if d.isCertain() then tag = "certain" else tag = "uncertain"
+    )
+  }
+}
+
+import MakeTest<AsDefinitionTest>