Wrap local vars in std::move (Clang 7 build fix)

This commit fixes diffblue#3238, a warning emitted by clang 7.0:

```
java_bytecode_convert_method.cpp:2924:10: error: local variable
'block' will be copied despite being returned by name
[-Werror,-Wreturn-std-move]
  return block;
         ^~~~~
java_bytecode_convert_method.cpp:2924:10: note: call 'std::move'
explicitly to avoid copying
  return block;
         ^~~~~
         std::move(block)
```

The fix is to wrap all such returned local variables in a call to
std::move().

Author: karkhaz

jbmc/src/java_bytecode/character_refine_preprocess.cpp

@@ -319,7 +319,7 @@ exprt character_refine_preprocesst::expr_of_high_surrogate(
   exprt u400=from_integer(0x0400, type);
 
   plus_exprt high_surrogate(uD800, div_exprt(minus_exprt(chr, u10000), u400));
-  return high_surrogate;
+  return std::move(high_surrogate);
 }
 
 /// Converts function call to an assignment of an expression corresponding to
@@ -496,7 +496,7 @@ exprt character_refine_preprocesst::expr_of_is_digit(
   or_exprt digit(
     or_exprt(latin_digit, or_exprt(arabic_indic_digit, extended_digit)),
     or_exprt(devanagari_digit, fullwidth_digit));
-  return digit;
+  return std::move(digit);
 }
 
 /// Converts function call to an assignment of an expression corresponding to
@@ -555,7 +555,7 @@ exprt character_refine_preprocesst::expr_of_is_identifier_ignorable(
      or_exprt(
       in_interval_expr(chr, 0x000E, 0x001B),
       in_interval_expr(chr, 0x007F, 0x009F)));
-  return ignorable;
+  return std::move(ignorable);
 }
 
 /// Converts function call to an assignment of an expression corresponding to
@@ -1235,7 +1235,7 @@ exprt character_refine_preprocesst::expr_of_to_lower_case(
     plus_exprt(chr, from_integer('a', type)), from_integer('A', type));
 
   if_exprt res(expr_of_is_ascii_upper_case(chr, type), transformed, chr);
-  return res;
+  return std::move(res);
 }
 
 /// Converts function call to an assignment of an expression corresponding to
@@ -1291,7 +1291,7 @@ exprt character_refine_preprocesst::expr_of_to_title_case(
           plus_9,
           chr))));
 
-  return res;
+  return std::move(res);
 }
 
 /// Converts function call to an assignment of an expression corresponding to
@@ -1328,7 +1328,7 @@ exprt character_refine_preprocesst::expr_of_to_upper_case(
     plus_exprt(chr, from_integer('A', type)), from_integer('a', type));
 
   if_exprt res(expr_of_is_ascii_lower_case(chr, type), transformed, chr);
-  return res;
+  return std::move(res);
 }
 
 /// Converts function call to an assignment of an expression corresponding to

jbmc/src/java_bytecode/java_bytecode_convert_method.cpp

@@ -231,7 +231,7 @@ const exprt java_bytecode_convert_methodt::variable(
     symbol_exprt result(identifier, t);
     result.set(ID_C_base_name, base_name);
     used_local_names.insert(result);
-    return result;
+    return std::move(result);
   }
   else
   {
@@ -1913,7 +1913,7 @@ codet java_bytecode_convert_methodt::convert_instructions(
   for(auto &block : root_block.statements())
     code.add(block);
 
-  return code;
+  return std::move(code);
 }
 
 codet java_bytecode_convert_methodt::convert_pop(
@@ -1983,7 +1983,7 @@ codet java_bytecode_convert_methodt::convert_switch(
   }
 
   code_switch.body() = code_block;
-  return code_switch;
+  return std::move(code_switch);
 }
 
 codet java_bytecode_convert_methodt::convert_monitorenterexit(
@@ -2006,7 +2006,7 @@ codet java_bytecode_convert_methodt::convert_monitorenterexit(
   call.add_source_location() = source_location;
   if(needed_lazy_methods && symbol_table.has_symbol(descriptor))
     needed_lazy_methods->add_needed_method(descriptor);
-  return call;
+  return std::move(call);
 }
 
 void java_bytecode_convert_methodt::convert_dup2(
@@ -2566,7 +2566,7 @@ codet java_bytecode_convert_methodt::convert_putstatic(
     bytecode_write_typet::STATIC_FIELD,
     symbol_expr.get_identifier());
   block.add(code_assignt(symbol_expr, op[0]));
-  return block;
+  return std::move(block);
 }
 
 codet java_bytecode_convert_methodt::convert_putfield(
@@ -2581,7 +2581,7 @@ codet java_bytecode_convert_methodt::convert_putfield(
     bytecode_write_typet::FIELD,
     arg0.get(ID_component_name));
   block.add(code_assignt(to_member(op[0], arg0), op[1]));
-  return block;
+  return std::move(block);
 }
 
 void java_bytecode_convert_methodt::convert_getstatic(
@@ -2722,7 +2722,7 @@ codet java_bytecode_convert_methodt::convert_iinc(
     plus_exprt(variable(arg0, 'i', address, CAST_AS_NEEDED), arg1_int_type));
   block.add(code_assign);
 
-  return block;
+  return std::move(block);
 }
 
 codet java_bytecode_convert_methodt::convert_ifnull(
@@ -2740,7 +2740,7 @@ codet java_bytecode_convert_methodt::convert_ifnull(
   code_branch.then_case().add_source_location() =
     address_map.at(label_number).source->source_location;
   code_branch.add_source_location() = location;
-  return code_branch;
+  return std::move(code_branch);
 }
 
 codet java_bytecode_convert_methodt::convert_ifnonull(
@@ -2758,7 +2758,7 @@ codet java_bytecode_convert_methodt::convert_ifnonull(
   code_branch.then_case().add_source_location() =
     address_map.at(label_number).source->source_location;
   code_branch.add_source_location() = location;
-  return code_branch;
+  return std::move(code_branch);
 }
 
 codet java_bytecode_convert_methodt::convert_if(
@@ -2780,7 +2780,7 @@ codet java_bytecode_convert_methodt::convert_if(
   code_branch.then_case().add_source_location().set_function(method_id);
   code_branch.add_source_location() = location;
   code_branch.add_source_location().set_function(method_id);
-  return code_branch;
+  return std::move(code_branch);
 }
 
 codet java_bytecode_convert_methodt::convert_if_cmp(
@@ -2809,7 +2809,7 @@ codet java_bytecode_convert_methodt::convert_if_cmp(
     address_map.at(label_number).source->source_location;
   code_branch.add_source_location() = location;
 
-  return code_branch;
+  return std::move(code_branch);
 }
 
 code_blockt java_bytecode_convert_methodt::convert_ret(
@@ -2889,7 +2889,7 @@ codet java_bytecode_convert_methodt::convert_store(
   code_assignt assign(var, toassign);
   assign.add_source_location() = location;
   block.add(assign);
-  return block;
+  return std::move(block);
 }
 
 codet java_bytecode_convert_methodt::convert_astore(
@@ -2921,7 +2921,7 @@ codet java_bytecode_convert_methodt::convert_astore(
   code_assignt array_put(element, op[2]);
   array_put.add_source_location() = location;
   block.add(array_put);
-  return block;
+  return std::move(block);
 }
 
 optionalt<exprt> java_bytecode_convert_methodt::convert_invoke_dynamic(

jbmc/src/java_bytecode/java_bytecode_instrument.cpp

@@ -133,7 +133,7 @@ codet java_bytecode_instrumentt::throw_exception(
   if_code.cond()=cond;
   if_code.then_case() = code_blockt({assign_new, code_expressiont(throw_expr)});
 
-  return if_code;
+  return std::move(if_code);
 }
 
 
@@ -205,7 +205,7 @@ codet java_bytecode_instrumentt::check_array_access(
   bounds_checks.add(create_fatal_assertion(ge_zero, low_check_loc));
   bounds_checks.add(create_fatal_assertion(lt_length, high_check_loc));
 
-  return bounds_checks;
+  return std::move(bounds_checks);
 }
 
 /// Checks whether `class1` is an instance of `class2` and throws
@@ -255,7 +255,7 @@ codet java_bytecode_instrumentt::check_class_cast(
   notequal_exprt op_not_null(null_check_op, null_pointer_exprt(voidptr));
   conditional_check.cond()=std::move(op_not_null);
   conditional_check.then_case()=std::move(check_code);
-  return conditional_check;
+  return std::move(conditional_check);
 }
 
 /// Checks whether `expr` is null and throws NullPointerException/
@@ -540,7 +540,7 @@ optionalt<codet> java_bytecode_instrumentt::instrument_expr(const exprt &expr)
   if(result==code_blockt())
     return {};
   else
-    return result;
+    return std::move(result);
 }
 
 /// Instruments `expr`

jbmc/src/java_bytecode/java_bytecode_parser.cpp

@@ -1572,7 +1572,7 @@ exprt java_bytecode_parsert::get_relement_value()
       {
         values.operands().push_back(get_relement_value());
       }
-      return values;
+      return std::move(values);
     }
 
   case 's':

jbmc/src/java_bytecode/java_static_initializers.cpp

@@ -627,7 +627,7 @@ codet get_thread_safe_clinit_wrapper_body(
     function_body.add(code_returnt());
   }
 
-  return function_body;
+  return std::move(function_body);
 }
 
 /// Produces the static initializer wrapper body for the given function.
@@ -702,7 +702,7 @@ codet get_clinit_wrapper_body(
 
   wrapper_body.then_case() = init_body;
 
-  return wrapper_body;
+  return std::move(wrapper_body);
 }
 
 
@@ -891,5 +891,5 @@ codet stub_global_initializer_factoryt::get_stub_initializer_body(
       update_in_placet::NO_UPDATE_IN_PLACE);
   }
 
-  return static_init_body;
+  return std::move(static_init_body);
 }

jbmc/src/java_bytecode/java_string_library_preprocess.cpp

@@ -1039,7 +1039,7 @@ codet java_string_library_preprocesst::make_float_to_string_code(
 
   // Return str
   code.add(code_returnt(str), loc);
-  return code;
+  return std::move(code);
 }
 
 /// Generate the goto code for string initialization.
@@ -1088,7 +1088,7 @@ codet java_string_library_preprocesst::make_init_function_from_call(
     code_assign_string_expr_to_java_string(arg_this, string_expr, symbol_table),
     loc);
 
-  return code;
+  return std::move(code);
 }
 
 /// Call a cprover internal function, assign the result to object `this` and
@@ -1114,7 +1114,7 @@ codet java_string_library_preprocesst::
     loc);
   const symbol_exprt arg_this(params[0].get_identifier(), params[0].type());
   code.add(code_returnt(arg_this), loc);
-  return code;
+  return std::move(code);
 }
 
 /// Call a cprover internal function and assign the result to object `this`.
@@ -1266,7 +1266,7 @@ exprt java_string_library_preprocesst::get_object_at_index(
     data_member, from_integer(index, java_int_type()), data_member.type());
   dereference_exprt data_at_index(
     data_pointer_plus_index, data_pointer_plus_index.type().subtype());
-  return data_at_index;
+  return std::move(data_at_index);
 }
 
 /// Helper for format function. Adds code:
@@ -1393,7 +1393,7 @@ exprt java_string_library_preprocesst::make_argument_for_format(
   }
 
   code.add(code_not_null, loc);
-  return arg_i_struct;
+  return std::move(arg_i_struct);
 }
 
 /// Used to provide code for the Java String.format function.
@@ -1451,7 +1451,7 @@ codet java_string_library_preprocesst::make_string_format_code(
       java_string, string_expr, symbol_table),
     loc);
   code.add(code_returnt(java_string), loc);
-  return code;
+  return std::move(code);
 }
 
 /// Used to provide our own implementation of the java.lang.Object.getClass()
@@ -1532,7 +1532,7 @@ codet java_string_library_preprocesst::make_object_get_class_code(
 
   // > return class1;
   code.add(code_returnt(class1), loc);
-  return code;
+  return std::move(code);
 }
 
 /// Provide code for a function that calls a function from the solver and simply
@@ -1558,7 +1558,7 @@ codet java_string_library_preprocesst::make_function_from_call(
     code_return_function_application(
       function_name, args, type.return_type(), symbol_table),
     loc);
-  return code;
+  return std::move(code);
 }
 
 /// Provide code for a function that calls a function from the solver and return
@@ -1600,7 +1600,7 @@ codet java_string_library_preprocesst::make_string_returning_function_from_call(
 
   // Return value
   code.add(code_returnt(str), loc);
-  return code;
+  return std::move(code);
 }
 
 /// Generates code for a function which copies a string object to a new string
@@ -1643,7 +1643,7 @@ codet java_string_library_preprocesst::make_copy_string_code(
 
   // Return value
   code.add(code_returnt(str), loc);
-  return code;
+  return std::move(code);
 }
 
 /// Generates code for a constructor of a string object from another string
@@ -1684,7 +1684,7 @@ codet java_string_library_preprocesst::make_copy_constructor_code(
     code_assign_string_expr_to_java_string(arg_this, string_expr, symbol_table),
     loc);
 
-  return code;
+  return std::move(code);
 }
 
 /// Generates code for the String.length method
@@ -1714,7 +1714,7 @@ codet java_string_library_preprocesst::make_string_length_code(
   code_returnt ret(get_length(deref, symbol_table));
   ret.add_source_location() = loc;
 
-  return ret;
+  return std::move(ret);
 }
 
 bool java_string_library_preprocesst::implements_function(

jbmc/src/java_bytecode/java_types.cpp

@@ -415,7 +415,7 @@ build_class_name(const std::string &src, const std::string &class_name_prefix)
       // Look for the next generic type info (if it exists)
       f_pos = src.find('<', e_pos + 1);
     } while(f_pos != std::string::npos);
-    return result;
+    return std::move(result);
   }
 
   return java_reference_type(symbol_type);

src/analyses/ai.cpp

@@ -82,7 +82,7 @@ jsont ai_baset::output_json(
     }
   }
 
-  return result;
+  return std::move(result);
 }
 
 /// Output the domains for a single function as JSON
@@ -113,7 +113,7 @@ jsont ai_baset::output_json(
     contents.push_back(location);
   }
 
-  return contents;
+  return std::move(contents);
 }
 
 /// Output the domains for the whole program as XML

src/analyses/ai_domain.cpp

@@ -19,7 +19,7 @@ jsont ai_domain_baset::output_json(const ai_baset &ai, const namespacet &ns)
   std::ostringstream out;
   output(out, ai, ns);
   json_stringt json(out.str());
-  return json;
+  return std::move(json);
 }
 
 xmlt ai_domain_baset::output_xml(const ai_baset &ai, const namespacet &ns) const

src/analyses/dependence_graph.cpp

@@ -299,7 +299,7 @@ jsont dep_graph_domaint::output_json(
     link["type"]=json_stringt("data");
   }
 
-  return graph;
+  return std::move(graph);
 }
 
 void dependence_grapht::add_dep(