linux-kernel - Re: limits.h in tools/

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Date: Tue, 23 Apr 2024 17:07:45 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: linux-kernel@...r.kernel.org, Willy Tarreau <w@....eu>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	Andrew Morton <akpm@...ux-foundation.org>, willy@...radead.org,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: limits.h in tools/

On Tue, Apr 23, 2024 at 10:29:31PM +0300, Andy Shevchenko wrote:
> On Tue, Apr 23, 2024 at 04:22:01PM -0300, Arnaldo Carvalho de Melo wrote:
> > On Tue, Apr 23, 2024 at 09:58:07PM +0300, Andy Shevchenko wrote:
> > > It seems tons of the code in tools include linux/limits.h. But I haven't found
> > > where do we copy it. Any pointers?

> > > Based on the discussion 20220603183231.15159C385A9@...p.kernel.org.

<SNIP>

> > But then is for building tools/, not the kernel, right? The discussion
> > you said this question was based on is about changing
> > include/linux/xarray.h, a kernel file, so should really be including
> > just kernel headers, files in the kernel source tree, outside tools/, I
> > don't see where what tools/ uses to build is relevant here? Can you
> > please elaborate?
> 
> I believe the tool in question is tools/testing/radix-tree/xarray.c.

And it is including stuff from the kernel directly, something we stopped
doing long ago in tools/ to avoid breakage when a kernel developer
changes kernel code:

⬢[acme@...lbox perf-tools-next]$ cd tools/testing/radix-tree/
⬢[acme@...lbox radix-tree]$ grep -A1 -- -I Makefile 
# SPDX-License-Identifier: GPL-2.0

CFLAGS += -I. -I../../include -I../../../lib -g -Og -Wall \
	  -D_LGPL_SOURCE -fsanitize=address -fsanitize=undefined
⬢[acme@...lbox radix-tree]$ realpath ../../include
/home/acme/git/perf-tools-next/tools/include

So far so good, no kernel files included, only tools/ stuff, but then:

⬢[acme@...lbox radix-tree]$ grep xarray *.c | grep include
xarray.c:#include "../../../lib/xarray.c"
xarray.c:#include "../../../lib/test_xarray.c"
⬢[acme@...lbox radix-tree]$ realpath ../../../lib/xarray.c
/home/acme/git/perf-tools-next/lib/xarray.c
⬢[acme@...lbox radix-tree]$

And this in turn will:

⬢[acme@...lbox radix-tree]$ grep ^#include  ../../../lib/xarray.c
#include <linux/bitmap.h>
#include <linux/export.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/xarray.h>
#include "radix-tree.h"
⬢[acme@...lbox radix-tree]$

Includes kernel headers, as it _is_ kernel code.

Perhaps since it does that we need to add -I../../../include to the
include path to really include kernel headers?

⬢[acme@...lbox radix-tree]$ pwd
/home/acme/git/perf-tools-next/tools/testing/radix-tree
⬢[acme@...lbox radix-tree]$ realpath ../../../include
/home/acme/git/perf-tools-next/include
⬢[acme@...lbox radix-tree]$

- Arnaldo