ComplexSelector to_css should probably not do recursion

[bzbarsky]

Currently it does:

    if let Some((ref next, ref combinator)) = self.next {
        next.to_css(dest)?;
        combinator.to_css(dest)?;
    }

which will run into crashes due to running out of stack; see https://bugzilla.mozilla.org/show_bug.cgi?id=475215

[highfive]

Hi! If you have any questions regarding this issue, feel free to make a comment here, or ask it in the #servo channel in IRC.

If you intend to work on this issue, then add @highfive: assign me to your comment, and I'll assign this to you. 😄

[emilio]

Happy to mentor this one.

[jdm]

Presumably we'll want to convert the code in https://dxr.mozilla.org/servo/rev/103e827948e4c3592ee93cbed8adf270588b559e/components/selectors/parser.rs#379-382 to use a loop instead?

[bzbarsky]

Yes, that is the general idea. The complication is that you want to loop backwards over a singly linked list.

Gecko does the obvious thing here: use a growable array with some preallocated stack storage (so you don't have to heap-allocate in common cases), walk the linked list adding things to the array, then walk the array backwards in a loop.

[tictakk]

Hi, I'm looking to contribute to servo. Is this being worked on/assigned?

[emilio]

Please take it if you want! Reply to this mentioning @highfive, or saying you want to take it, and we'll assign it to you :)

[tictakk]

Okay, awesome. @highfive: assign me

[highfive]

Hey @tictakk! Thanks for your interest in working on this issue. It's now assigned to you!

[highfive]

cc @emilio

[wafflespeanut]

@tictakk Any news on this?

[tictakk]

@wafflespeanut Spent the weekend finishing a school project and brushing up on Rust. I'll be expeditious as possible.

[wafflespeanut]

Great!

[tictakk]

@emilio Hey, I think I could use some of that mentorship you mentioned. Should I be creating a vector of each child and looping to_css() one at a time?

[emilio]

Yes, that sounds right. We could consider creating a SmallVec to avoid heap allocation in the common case :)