GNU bug report logs - #51021
detect loops in module/package graph

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From: Ludovic Courtès <ludo <at> gnu.org>
To: zimoun <zimon.toutoune <at> gmail.com>
Cc: Mark H Weaver <mhw <at> netris.org>, 51021 <at> debbugs.gnu.org
Subject: bug#51021: detect loops in module/package graph
Date: Tue, 12 Oct 2021 11:47:39 +0200

Hi,

zimoun <zimon.toutoune <at> gmail.com> skribis:

> What Mark had implemented [1] works for any directed graph.  What do
> you mean by "top-level references"?

Reference to variables coming from one module of an SCC that appear at
the top level of another module in the SCC.

>> Chris Baines proposed a patch a while back to report those, though I
>> can’t find it anymore.  IIRC, the difficulty was in making sure cycle
>> detection would not be too expensive, and in keeping a readable style.
>
> From my memories about Graph Theory, the algorithm Mark is proposing
> is an efficient way to detect cycles

What I meant is that ‘package-derivation’ traverses the package graph,
so it’s a natural place to add cycle detection.

But since ‘package-derivation’ is so central, care must be taken about
the performance hit and about its readability.

Thanks,
Ludo’.

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