goto-harness: use new symbolt constructors

To the extent possible, apply resource-acquisition-is-initialisation.
The constructors ensure that at least the most essential fields (name,
type, mode) are set.

Author: tautschnig

src/goto-harness/memory_snapshot_harness_generator.cpp

@@ -404,14 +404,13 @@ void memory_snapshot_harness_generatort::generate(
 
   // Create harness function symbol
 
-  symbolt harness_function_symbol;
-  harness_function_symbol.name = harness_function_name;
+  symbolt harness_function_symbol{
+    harness_function_name,
+    code_typet({}, empty_typet()),
+    called_function_symbol->mode};
   harness_function_symbol.base_name = harness_function_name;
   harness_function_symbol.pretty_name = harness_function_name;
-
   harness_function_symbol.is_lvalue = true;
-  harness_function_symbol.mode = called_function_symbol->mode;
-  harness_function_symbol.type = code_typet({}, empty_typet());
   harness_function_symbol.value = harness_function_body;
 
   // Add harness function to goto model and symbol table

src/goto-harness/recursive_initialization.cpp

@@ -377,12 +377,13 @@ symbol_exprt recursive_initializationt::get_malloc_function()
   auto malloc_sym = goto_model.symbol_table.lookup("malloc");
   if(malloc_sym == nullptr)
   {
-    symbolt new_malloc_sym;
-    new_malloc_sym.type = code_typet{code_typet{
-      {code_typet::parametert{size_type()}}, pointer_type(empty_typet{})}};
-    new_malloc_sym.name = new_malloc_sym.pretty_name =
-      new_malloc_sym.base_name = "malloc";
-    new_malloc_sym.mode = initialization_config.mode;
+    symbolt new_malloc_sym{
+      "malloc",
+      code_typet{
+        {code_typet::parametert{size_type()}}, pointer_type(empty_typet{})},
+      initialization_config.mode};
+    new_malloc_sym.pretty_name = "malloc";
+    new_malloc_sym.base_name = "malloc";
     goto_model.symbol_table.insert(new_malloc_sym);
     return new_malloc_sym.symbol_expr();
   }
@@ -634,12 +635,13 @@ symbol_exprt recursive_initializationt::get_free_function()
   auto free_sym = goto_model.symbol_table.lookup("free");
   if(free_sym == nullptr)
   {
-    symbolt new_free_sym;
-    new_free_sym.type = code_typet{code_typet{
-      {code_typet::parametert{pointer_type(empty_typet{})}}, empty_typet{}}};
-    new_free_sym.name = new_free_sym.pretty_name = new_free_sym.base_name =
-      "free";
-    new_free_sym.mode = initialization_config.mode;
+    symbolt new_free_sym{
+      "free",
+      code_typet{
+        {code_typet::parametert{pointer_type(empty_typet{})}}, empty_typet{}},
+      initialization_config.mode};
+    new_free_sym.pretty_name = "free";
+    new_free_sym.base_name = "free";
     goto_model.symbol_table.insert(new_free_sym);
     return new_free_sym.symbol_expr();
   }