linux-kernel - Re: [PATCH 00/40] Memory allocation profiling

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Message-ID: <20230508205939.0b5b485c@meshulam.tesarici.cz>
Date:   Mon, 8 May 2023 20:59:39 +0200
From:   Petr Tesařík <petr@...arici.cz>
To:     Kent Overstreet <kent.overstreet@...ux.dev>
Cc:     Michal Hocko <mhocko@...e.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
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Subject: Re: [PATCH 00/40] Memory allocation profiling

On Mon, 8 May 2023 12:28:52 -0400
Kent Overstreet <kent.overstreet@...ux.dev> wrote:

> On Mon, May 08, 2023 at 06:09:13PM +0200, Petr Tesařík wrote:
> > Sure, although AFAIK the index does not cover all possible config
> > options (so non-x86 arch code is often forgotten). However, that's the
> > less important part.
> > 
> > What do you do if you need to hook something that does conflict with an
> > existing identifier?  
> 
> As already happens in this patchset, rename the other identifier.
> 
> But this is C, we avoid these kinds of conflicts already because the
> language has no namespacing

This statement is not accurate, but I agree there's not much. Refer to
section 6.2.3 of ISO/IEC9899:2018 (Name spaces of identifiers).

More importantly, macros also interfere with identifier scoping, e.g.
you cannot even have a local variable with the same name as a macro.
That's why I dislike macros so much.

But since there's no clear policy regarding macros in the kernel, I'm
merely showing a downside; it's perfectly fine to write kernel code
like this as long as the maintainers agree that the limitation is
acceptable and outweighed by the benefits.

Petr T

> it's going to be a pretty rare situtaion
> going forward. Most of the hooking that will be done is done with this
> patchset, and there was only one identifier that needed to be renamed.
>