linux-kernel - [PATCH 2/3] auto: add "auto" keyword as alias for __auto

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Message-Id: <20230516164947.86543-2-adobriyan@gmail.com>
Date:   Tue, 16 May 2023 19:49:46 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, adobriyan@...il.com
Subject: [PATCH 2/3] auto: add "auto" keyword as alias for __auto_type

It has similar semantics to "auto" keyword from a language
which can not be named on this mailing list, in particular:

	{
		int a;
		const auto b = a; // const char b = a;
		b = 1;	// compile error
	}
	{
		char a;
		auto b = a; // char b = a;
		// no integer promotions
		static_assert(sizeof(b) == 1);
	}
	{
		int a;
		const auto p = &a; // int *const p = &a;
		*p = 1;	// works because const is applied only to top-level
	}

It can be used to save on macroexpansion inside macro forests which
use typeof() somewhere deep enough. It is cool regardless.

Use "auto" in your code today!

gcc 5.1 supports __auto_type.

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---
 Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Makefile b/Makefile
index 10fcc64fcd1f..d316924a466a 100644
--- a/Makefile
+++ b/Makefile
@@ -570,6 +570,7 @@ KBUILD_CFLAGS += -Werror=return-type
 KBUILD_CFLAGS += -Werror=strict-prototypes
 KBUILD_CFLAGS += -Wno-format-security
 KBUILD_CFLAGS += -Wno-trigraphs
+KBUILD_CFLAGS += -Dauto=__auto_type
 
 KBUILD_CPPFLAGS := -D__KERNEL__
 KBUILD_RUSTFLAGS := $(rust_common_flags) \
-- 
2.40.1