Layout Code Reviewer Checklist

General

Security issues

  • Watch for raw pointers that may have their data deleted out from under them. Examples:

    • If you ever have a raw pointer to a dynamically allocated object, it’s good to scrutinize whether the object might be destroyed before the last possible use of the raw pointer. For example: if you have a local variable that points to an object that’s owned by a frame’s property table, then consider whether the frame might remove/replace the property-table entry (or whether the frame itself might be destroyed) inside any of the function calls that happen while the local pointer is in scope.

    • Be aware that layout flushes (e.g. doc->FlushPendingNotifications(FlushType::Layout)) can synchronously cause the frame tree (and even the document!) to be destroyed. Specifically: a layout flush can synchronously cause resize events to fire; and the event-listeners for those events can run arbitrary script, which could e.g. remove the iframe element that’s hosting the document whose layout we’re in the midst of flushing; and that can cause that document to be immediately destroyed, if there aren’t any other strong references keeping it alive.