Re: #pragma once?

[Michal Marek]

On 2014-01-07 10:48, Geert Uytterhoeven wrote:
> Furthermore some userspace may rely on doing #define XXX to avoid
> including a specific kernel header (yes, it's ugly).

This pattern is also sometimes used:
$ head -6 include/linux/spinlock_up.h
#ifndef __LINUX_SPINLOCK_UP_H
#define __LINUX_SPINLOCK_UP_H

#ifndef __LINUX_SPINLOCK_H
# error "please don't include this file directly"
#endif

And there is nothing ugly about it. So #pragma once is probably a good
idea for most headers that are not exposed to userspace. But making it a
requirement in scripts/checkpatch.pl or Documentation/CodingStyle means
that it will become hard to defend the few legitimate uses of ifndef
guards against people who have a printed copy of checkpatch.pl under
their pillow.

Michal
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