Bug 72 – Adding additional assertions in Buffer uncovers bugs

Bug 72 - Adding additional assertions in Buffer uncovers bugs


Summary:	Adding additional assertions in Buffer uncovers bugs

Status:	RESOLVED FIXED

Product:	ns-3
Classification:	Unclassified
Component:	core
Version:	pre-release
Hardware:	PC Linux

Importance:	P1 blocker
Assigned To:	ns-bugs

URL:
Keywords:

Depends on:
Blocks:
	Show dependency tree / graph

Reported:	2007-09-06 07:01 UTC by Gustavo J. A. M. Carneiro
Modified:	2007-09-10 12:55 UTC (History)
CC List:	0 users

See Also:

Attachments
patch to add the additional assertions (with it, waf check triggers an assertion) (1.21 KB, patch) 2007-09-06 07:02 UTC, Gustavo J. A. M. Carneiro	Details \| Diff
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Description Gustavo J. A. M. Carneiro 2007-09-06 07:01:40 UTC

I found the assertion:
    NS_ASSERT (m_start <= m_data->m_initialStart);
in Buffer::AddAtStart being triggered for my OLSR code.

I must say that I don't understand the Buffer implementation.  However, that particular assertion is present at the very start of Buffer::AddAtStart and doesn't check the parameter, which leads me to conclude it is an internal consistency check on the buffer state, thus an invariant.  Invariants must be observed everywhere, and so I added the assertion in a few more places and was able to trigger the assertion from the unit tests.  Either the assertion is wrong or there is another bug inside Buffer.

Comment 1 Gustavo J. A. M. Carneiro 2007-09-06 07:02:41 UTC

Created attachment 52 [details]
patch to add the additional assertions (with it, waf check triggers an assertion)

Comment 2 Mathieu Lacage 2007-09-10 12:55:10 UTC

reduced testcase.

  p = Packet (10);
  ADD_HEADER (p, 8);
  ADD_TRAILER (p, 8);
  ADD_TRAILER (p, 8);
  p.RemoveAtStart (8+10+8);
  CHECK_HISTORY (p, 1, 8);

I have a fix in a private repo but I need to clean it up before inclusion.