Bug 1369 – [LLVM] error: comparison of unsigned expression < 0 is always false

Bug 1369 - [LLVM] error: comparison of unsigned expression < 0 is always false


Summary:	[LLVM] error: comparison of unsigned expression < 0 is always false

Status:	RESOLVED FIXED

Product:	ns-3
Classification:	Unclassified
Component:	dsdv
Version:	ns-3-dev
Hardware:	All All

Importance:	P5 normal
Assigned To:	Hemanth Narra

URL:
Keywords:

Depends on:
Blocks:	1345
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Reported:	2012-02-22 06:24 UTC by Gustavo J. A. M. Carneiro
Modified:	2012-03-18 07:11 UTC (History)
CC List:	2 users (show)

See Also:

Attachments
Removes the if that is never executed (645 bytes, patch) 2012-03-12 08:20 UTC, Daniel Camara	Details \| Diff
patch to fix bug 1369 in dsdv-routing-protocol.cc (462 bytes, patch) 2012-03-17 21:00 UTC, Hemanth Narra	Details \| Diff
Show Obsolete (1) Add an attachment (proposed patch, testcase, etc.)

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Description Gustavo J. A. M. Carneiro 2012-02-22 06:24:01 UTC

With clang++ 2.9:

[ 856/1334] cxx: src/dsdv/model/dsdv-routing-protocol.cc -> build/src/dsdv/model/dsdv-routing-protocol.cc.1.o
../src/dsdv/model/dsdv-routing-protocol.cc:843:25: error: comparison of unsigned expression < 0 is always false
      [-Werror,-Wtautological-compare]
  if (allRoutes.size () < 0)
      ~~~~~~~~~~~~~~~~~ ^ ~
1 error generated.

Comment 1 Daniel Camara 2012-03-12 08:20:57 UTC

Created attachment 1355 [details]
Removes the if that is never executed

Patch to solve the "comparison of unsigned expression < 0 is always false"  error message of clang. The path removes the if, this solution should be evaluate by the maintainer of the module to be sure it is correct.

Comment 2 Tommaso Pecorella 2012-03-12 13:21:00 UTC

I disagree with the patch.

The correct fix is:
  if (allRoutes.size () == 0)
    {
      return;
    }

or, better
  if (allRoutes.empty())
    {
      return;
    }

On the other hand, later the map is traversed with an iterator. Thus removing the if() is not introducing a bug, it's just removing an optimization (it wasn't working anyway right now).

T.

Comment 3 Hemanth Narra 2012-03-17 21:00:57 UTC

Created attachment 1361 [details]
patch to fix bug 1369 in dsdv-routing-protocol.cc

Yes, I agree. we need this if statement. Here is the patch that fixes this bug.

Comment 4 Hemanth Narra 2012-03-17 21:02:48 UTC

Marking this bug as fixed. Daniel, can you please upload this patch to the repository?

Comment 5 Tommaso Pecorella 2012-03-18 07:11:18 UTC

Pushed to changeset 7767 - 657d0877064e