Re: Dead code by symbols

From: David Hildenbrand
Date: Tue Sep 17 2024 - 07:39:51 EST


On 16.09.24 14:33, Dr. David Alan Gilbert wrote:
Hi David,
A while ago we were chatting about me spotting dead structs, and
you wondered if it might be possible to spot dead functions that
were exported from an object but never used - and I've been trying
it for the last few days.

I'm pretty early on, but it's already got some fun things:

Cool, stuff! :)


https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=6a36d828bdef0e02b1e6c12e2160f5b83be6aab5
Core code not used for ~20 years

https://lore.kernel.org/lkml/1690847.1726346402@xxxxxxxxxxxxxxxxxxxxxx/
A bug! A recently added function that lost the place it was wired up
so was currently unused.

That is really nice!


https://lore.kernel.org/lkml/ZuXOWjvVYa64c1-5@gallifrey/
A few small dead files.

Now, it does take some more guesswork, for example an unused function
which was added a couple of years back, might be something that's
there for consistency,

I know people will find reasons to do something like that, but we really *shouldn't* be maintaining / dragging along dead code that nobody might ever use.

might have been forgotten to be wired up,

Forgotten as in "BUG" or as in "ran out of steam" ?

or might just be something that's going to be used but the
authors haven't got to it yet, e.g.
https://lore.kernel.org/lkml/ZuRGRKU9bjgC52mD@gallifrey/

Yes, that' a valid case.


My patience varies from Ooh core code, to meh old driver to very meh
for old undead staging code.

:)


I've got some nasty awk which kind of works some of the time;
but it does require a lot of handholding; often things like inlining
isn't spotted so gives a false positive, and I'm only looking at
the objects from a single architecture, so again have to grep
for the symbol name to make sure it's not used by a different
architecture build.

And heck, I wish git log -G was faster.

:)


Anyway, thanks for the suggestion!

Glad you're able to spot some nice (+fun, otherwise you wouldn't be doing it ;) ) things!

--
Cheers,

David / dhildenb