[RTEMS Project] #3360: 4.10: _Chain_Is_first/last overshoot

[RTEMS trac]

#3360: 4.10: _Chain_Is_first/last overshoot
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  Reporter:  Gedare  |      Owner:  Gedare
      Type:  defect  |     Status:  assigned
  Priority:  normal  |  Milestone:  4.10.3
 Component:  score   |    Version:  4.10
  Severity:  normal  |   Keywords:
Blocked By:          |   Blocking:
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 A user reported a possible problem with the implementation of the
 _Chain_Is_first/last functions:
 -------- Original Message --------
 Subject: [Milkymist-devel] [PATCH, tentative] RTEMS: _Chain_Is_first/last
 overshoot
 Date: Wed, 9 Nov 2011 16:53:53 -0300
 From: Werner Almesberger <werner at almesberger.net>
 Reply-To: Milkymist One, Milkymist SoC and Flickernoise developers' list
 <devel at lists.milkymist.org>
 To: Milkymist One, Milkymist SoC and Flickernoise developers' list
 <devel at lists.milkymist.org>

 Doubly-linked lists ("chains") in RTEMS have a "control" block that
 looks like the next/prev link pair in an element. The list elements
 link both ways to this control block.

 _Chain_Is_first and _Chain_Is_last only probed if the link to the
 next element - which would be the control block - is non-NULL.
 Telling by the function description and given that there are already
 functions called _Chain_Is_head and _Chain_Is_tail (which could be
 simplified), this is probably not the intended behaviour.

 This also affects the aliases rtems_chain_is_first and
 rtems_chain_is_last.

 These functions are not used a lot and I haven't seen any immediate
 effect on M1 after changing them, so I can't say whether this patch
 may unearth other problems.

 - Werner

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Ticket URL: <http://devel.rtems.org/ticket/3360>
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