From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47481) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1geyoX-0003CZ-Bx for qemu-devel@nongnu.org; Thu, 03 Jan 2019 03:57:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1geyoU-00015w-H7 for qemu-devel@nongnu.org; Thu, 03 Jan 2019 03:57:17 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54612) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1geyoU-0000u8-9P for qemu-devel@nongnu.org; Thu, 03 Jan 2019 03:57:14 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7DEE9142BEF for ; Thu, 3 Jan 2019 08:56:59 +0000 (UTC) From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Date: Thu, 3 Jan 2019 09:56:34 +0100 Message-Id: <20190103085638.17600-2-philmd@redhat.com> In-Reply-To: <20190103085638.17600-1-philmd@redhat.com> References: <20190103085638.17600-1-philmd@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PATCH v5 1/5] qemu/compiler: Define QEMU_NONSTRING List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: "Dr. David Alan Gilbert" , Thomas Huth , David Hildenbrand , Igor Mammedov , Paolo Bonzini , Markus Armbruster , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Eric Blake , "Michael S. Tsirkin" , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= GCC 8 introduced the -Wstringop-truncation checker to detect truncation b= y the strncat and strncpy functions (closely related to -Wstringop-overflow= , which detect buffer overflow by string-modifying functions declared in ). In tandem of -Wstringop-truncation, the "nonstring" attribute was added: The nonstring variable attribute specifies that an object or member declaration with type array of char, signed char, or unsigned char, or pointer to such a type is intended to store character arrays that do not necessarily contain a terminating NUL. This is useful in detecti= ng uses of such arrays or pointers with functions that expect NUL-terminat= ed strings, and to avoid warnings when such an array or pointer is used as an argument to a bounded string manipulation function such as strncpy. From the GCC manual: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable= -Attributes.html#index-nonstring-variable-attribute Add the QEMU_NONSTRING macro which checks if the compiler supports this attribute. Suggested-by: Michael S. Tsirkin Reviewed-by: Eric Blake Reviewed-by: Michael S. Tsirkin Reviewed-by: Richard Henderson Reviewed-by: Thomas Huth Signed-off-by: Philippe Mathieu-Daud=C3=A9 --- v4: reordered the commit description to make sens (eblake) Note this trigger the following checkpatch warning (patchew) which I'm ignoring because this is consistent with how the rest of this file uses: WARNING: architecture specific defines should be avoided #50: FILE: include/qemu/compiler.h:163: +#if __has_attribute(nonstring) --- include/qemu/compiler.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h index 261842beae..2d8f507c73 100644 --- a/include/qemu/compiler.h +++ b/include/qemu/compiler.h @@ -151,6 +151,21 @@ # define QEMU_ERROR(X) #endif =20 +/* + * The nonstring variable attribute specifies that an object or member + * declaration with type array of char or pointer to char is intended + * to store character arrays that do not necessarily contain a terminati= ng + * NUL character. This is useful in detecting uses of such arrays or poi= nters + * with functions that expect NUL-terminated strings, and to avoid warni= ngs + * when such an array or pointer is used as an argument to a bounded str= ing + * manipulation function such as strncpy. + */ +#if __has_attribute(nonstring) +# define QEMU_NONSTRING __attribute__((nonstring)) +#else +# define QEMU_NONSTRING +#endif + /* Implement C11 _Generic via GCC builtins. Example: * * QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x) --=20 2.17.2