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Sat, 14 Nov 2026 08:57:07 -0800 (PST) Received: from SafoStation ([31.40.65.49]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5c1712dad26sm1792051e87.8.2026.11.14.08.57.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Nov 2026 08:57:07 -0800 (PST) From: Safocl Stollmannovic To: Petr Mladek , John Ogness , Steven Rostedt , Sergey Senozhatsky Cc: linux-kernel@vger.kernel.org, printk@lists.linux.dev Subject: [PATCH v3 11/14] printk: fix duplicate extern declarations Date: Sat, 14 Nov 2026 20:55:51 +0400 Message-ID: <20261114165612.368785-12-safocl88@gmail.com> X-Mailer: git-send-email 2.56.1 In-Reply-To: <20261114165612.368785-1-safocl88@gmail.com> References: <20261114165612.368785-1-safocl88@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Compiling a kernel module with a C++ compiler results in a "duplicate extern specifier" error. This occurs because the code contains `extern asmlinkage`, and `asmlinkage` expands to `extern C` when processed by a C++ compiler. Since the code already contains sections that respond to a C++ compiler, I believe it is a perfectly valid approach to gradually move toward a state where kernel modules can be compiled by a C++ compiler without any issues. The `extern` specifier must be removed. Link: https://bugzilla.kernel.org/show_bug.cgi?id=222257 Signed-off-by: Safocl Stollmannovic --- include/linux/printk.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/printk.h b/include/linux/printk.h index f594c1266..09a28181e 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -136,7 +136,7 @@ struct va_format { }) #ifdef CONFIG_EARLY_PRINTK -extern asmlinkage __printf(1, 2) +asmlinkage __printf(1, 2) void early_printk(const char *fmt, ...); #else static inline __printf(1, 2) __cold @@ -200,8 +200,8 @@ void __init setup_log_buf(int early); __printf(1, 2) void dump_stack_set_arch_desc(const char *fmt, ...); void dump_stack_print_info(const char *log_lvl); void show_regs_print_info(const char *log_lvl); -extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold; -extern asmlinkage void dump_stack(void) __cold; +asmlinkage void dump_stack_lvl(const char *log_lvl) __cold; +asmlinkage void dump_stack(void) __cold; void printk_trigger_flush(void); void console_try_replay_all(void); void printk_legacy_allow_panic_sync(void); -- 2.56.1