From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on gnuweeb.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=ALL_TRUSTED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NO_DNS_FOR_FROM,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.6 Received: from localhost.localdomain (unknown [138.197.159.143]) by gnuweeb.org (Postfix) with ESMTPSA id 647107E7F6; Mon, 9 May 2022 06:54:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1652079293; bh=S0U9M32154HScyfLSnF1HZ9qZvAR0EcCgcUUKQmmE44=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WHfbcEyoxuzZ2fSeGRnGn8fybzzOrakqv0xyTMDpZZADLUDgiaQ5U02yjbXyKtgV+ IkWPjQvCgsAOUuuQ7J2zbiPNvpxcLTZ/4BWH/81NNxvhWGc2TJhYfi10JS74vBa9BC 303lJS1TaaNn4Rh512aK20HkxZgVLy/+RjWzhnOlYxJspgX06Bb4yclmPg/nBA5/+w 5Yr8o8o3jAWurcDjuyrFgQjC3n811L4WZmdzEPqlUErAPppZF+qZaavLhsyHn1F6P8 sesXfFJujp1R0DbYiZJmJ7XTwesHLxywUqLkUTTNW6zVnhB3Jj6LeUseHuMVg0XkU+ EFzkaxsQsz+yQ== From: Alviro Iskandar Setiawan To: Ammar Faizi Cc: GNU/Weeb Mailing List , Linux Kernel Mailing List , Alviro Iskandar Setiawan Subject: [PATCH 1/1] tools/nolibc/stdio: Add format attribute to enable printf warnings Date: Mon, 9 May 2022 06:54:45 +0000 Message-Id: <20220509065445.3912334-2-alviro.iskandar@gnuweeb.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20220509065445.3912334-1-alviro.iskandar@gnuweeb.org> References: <20220509065445.3912334-1-alviro.iskandar@gnuweeb.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit List-Id: When we use printf and fprintf functions from nolibc, we don't get any warning from the compiler if we have wrong arguments, for example the following calls will compile silently: ``` printf("%s %s\n", "aaa"); fprintf(stdout, "%s %s\n", "xxx", 1); ``` Those calls are undefined behavior. We can catch it at compile time by adding format attribute to those function declarations. After this patch, we get the following warnings: ``` warning: format `%s` expects a matching `char *` argument [-Wformat=] warning: format `%s` expects argument of type `char *`, but argument 4 has type `int` [-Wformat=] ``` Signed-off-by: Alviro Iskandar Setiawan --- tools/include/nolibc/stdio.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h index 15dedf8d0902..009dd6ae68f2 100644 --- a/tools/include/nolibc/stdio.h +++ b/tools/include/nolibc/stdio.h @@ -273,7 +273,7 @@ int vfprintf(FILE *stream, const char *fmt, va_list args) return written; } -static __attribute__((unused)) +static __attribute__((unused)) __attribute__((format(printf, 2, 3))) int fprintf(FILE *stream, const char *fmt, ...) { va_list args; @@ -285,7 +285,7 @@ int fprintf(FILE *stream, const char *fmt, ...) return ret; } -static __attribute__((unused)) +static __attribute__((unused)) __attribute__((format(printf, 1, 2))) int printf(const char *fmt, ...) { va_list args; -- Alviro Iskandar Setiawan