Add unit test

The unit test checks whether the correct function is called. It is therefor more
precise than the regression test `virtual10`.

Author: Matthias Güdemann

unit/java_bytecode/java_virtual_functions/A.class

@@ -0,0 +1,35 @@
+interface A {
+  public int f();
+}
+interface B {
+  public int g();
+}
+
+class O {
+  public String toString() {
+    return "O";
+  }
+}
+
+class D extends O implements A, B {
+  public int f() {
+    return 0;
+  }
+  public int g() {
+    return 1;
+  }
+}
+
+class C extends D {
+  public String toString() {
+    return "C";
+  }
+}
+
+class E {
+  C c;
+  D d;
+  String f(Object o) {
+    return o.toString();
+  }
+}

unit/java_bytecode/java_virtual_functions/B.class

@@ -0,0 +1,120 @@
+/*******************************************************************\
+
+ Module: Unit tests for java_types
+
+ Author: DiffBlue Limited. All rights reserved.
+
+\*******************************************************************/
+
+#include <testing-utils/catch.hpp>
+#include <testing-utils/load_java_class.h>
+#include <testing-utils/require_goto_statements.h>
+
+#include <goto-programs/goto_convert_functions.h>
+#include <goto-programs/remove_virtual_functions.h>
+#include <util/config.h>
+
+#include <util/std_expr.h>
+
+void check_function_call(
+  const equal_exprt &eq_expr,
+  const irep_idt &class_name,
+  const irep_idt &function_name,
+  const goto_programt::targetst &targets)
+{
+  REQUIRE(eq_expr.op0().id() == ID_constant);
+  REQUIRE(eq_expr.op0().type().id() == ID_string);
+  REQUIRE(to_constant_expr(eq_expr.op0()).get_value() == class_name);
+
+  REQUIRE(targets.size() == 1);
+
+  for(const auto &target : targets)
+  {
+    REQUIRE(target->type == goto_program_instruction_typet::FUNCTION_CALL);
+    const code_function_callt call = to_code_function_call(target->code);
+    REQUIRE(call.function().id() == ID_symbol);
+    REQUIRE(to_symbol_expr(call.function()).get_identifier() == function_name);
+  }
+}
+
+SCENARIO(
+  "load class with virtual method call, resolve to all valid calls",
+  "[core][java_bytecode][virtual_functions]")
+{
+  config.set_arch("none");
+  GIVEN("A class with a call to java.lang.Object.toString()")
+  {
+    const symbol_tablet &symbol_table =
+      load_java_class("E", "./java_bytecode/java_virtual_functions", "E.f");
+
+    const std::string function_name =
+      "java::E.f:(Ljava/lang/Object;)Ljava/lang/String;";
+
+    WHEN("The entry point function is generated")
+    {
+      symbol_tablet new_table(symbol_table);
+      null_message_handlert null_output;
+      goto_functionst new_goto_functions;
+      goto_convert(new_table, new_goto_functions, null_output);
+      remove_virtual_functions(new_table, new_goto_functions);
+
+      bool found_function = false;
+      for(const auto &fun : new_goto_functions.function_map)
+      {
+        if(fun.first == function_name)
+        {
+          const goto_programt &goto_program = fun.second.body;
+          found_function = true;
+          for(const auto &instruction : goto_program.instructions)
+          {
+            // There should be two guarded GOTOs with non-constant guards. One
+            // branching for class C and one for class D or O.
+            if(instruction.type == goto_program_instruction_typet::GOTO)
+            {
+              if(instruction.guard.id() == ID_equal)
+              {
+                THEN("Class C should call its specific method")
+                {
+                  const equal_exprt &eq_expr = to_equal_expr(instruction.guard);
+                  check_function_call(
+                    eq_expr,
+                    "java::C",
+                    "java::C.toString:()Ljava/lang/String;",
+                    instruction.targets);
+                }
+              }
+
+              else if(instruction.guard.id() == ID_or)
+              {
+                THEN("Classes D and O should both call O.toString()")
+                {
+                  const or_exprt &disjunction = to_or_expr(instruction.guard);
+                  REQUIRE(
+                    (disjunction.op0().id() == ID_equal &&
+                     disjunction.op1().id() == ID_equal));
+                  const equal_exprt &eq_expr0 =
+                    to_equal_expr(disjunction.op0());
+                  const equal_exprt &eq_expr1 =
+                    to_equal_expr(disjunction.op1());
+
+                  check_function_call(
+                    eq_expr0,
+                    "java::D",
+                    "java::O.toString:()Ljava/lang/String;",
+                    instruction.targets);
+                  check_function_call(
+                    eq_expr1,
+                    "java::O",
+                    "java::O.toString:()Ljava/lang/String;",
+                    instruction.targets);
+                }
+              }
+            }
+          }
+        }
+      }
+
+      REQUIRE(found_function);
+    }
+  }
+}