servo/tests/unit/script/size_of.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use script::test::size_of;

// Macro so that we can stringify type names
// I'd really prefer the tests themselves to be run at plugin time,
// however rustc::middle doesn't have access to the full type data
macro_rules! sizeof_checker (
    ($testname: ident, $t: ident, $known_size: expr) => (
        #[test]
        fn $testname() {
            let new = size_of::$t();
            let old = $known_size;
            if new < old {
                panic!("Your changes have decreased the stack size of commonly used DOM struct {} from {} to {}. \
                        Good work! Please update the size in tests/unit/script/size_of.rs.",
                        stringify!($t), old, new)
            } else if new > old {
                panic!("Your changes have increased the stack size of commonly used DOM struct {} from {} to {}. \
                        These structs are present in large quantities in the DOM, and increasing the size \
                        may dramatically affect our memory footprint. Please consider choosing a design which \
                        avoids this increase. If you feel that the increase is necessary, \
                        update to the new size in tests/unit/script/size_of.rs.",
                        stringify!($t), old, new)
        }
    });
);

// Update the sizes here
sizeof_checker!(size_event_target, EventTarget, 48);
sizeof_checker!(size_node, Node, 160);
sizeof_checker!(size_element, Element, 320);
sizeof_checker!(size_htmlelement, HTMLElement, 336);
sizeof_checker!(size_div, HTMLDivElement, 336);
sizeof_checker!(size_span, HTMLSpanElement, 336);
sizeof_checker!(size_text, Text, 192);
sizeof_checker!(size_characterdata, CharacterData, 192);
sizeof_checker!(size_servothreadsafelayoutnode, ServoThreadSafeLayoutNode, 16);

// We use these types in the parallel traversal. They should stay pointer-sized.
sizeof_checker!(size_sendelement, SendElement, 8);
sizeof_checker!(size_sendnode, SendNode, 8);