760812 - correct bitflags for objects allocated by size in nsPresArena

Status: RESOLVED FIXED

(Core :: Layout, defect)

Description

[Nathan Froyd [:froydnj]]

Attachment: patch

nsPresArena.h says:

  enum ObjectID {
    nsLineBox_id = nsQueryFrame::NON_FRAME_MARKER,

    // The PresArena implementation uses this bit to distinguish objects
    // allocated by size from objects allocated by type ID (that is, frames
    // using AllocateByFrameID and other objects using AllocateByObjectID).
    // It should not collide with any Object ID (above) or frame ID (in
    // nsQueryFrame.h).  It is not 0x80000000 to avoid the question of
    // whether enumeration constants are signed.
    NON_OBJECT_MARKER = 0x40000000
  };

but the actual implementation of AllocateBySize wrongly uses nsQueryFrame::NON_FRAME_MARKER instead of NON_OBJECT_MARKER.  (nsPresArena.cpp doesn't even use NON_OBJECT_MARKER currently.)  If we were to add more ObjectIDs for better arena allocation statistics, we'd eventually run into problems, though it would take a while.  Let's fix this.

Comment 1

[Nathan Froyd [:froydnj]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/4cb9c03a3804

Comment 2

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/4cb9c03a3804