From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47710) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gcwl0-0001GL-Fa for qemu-devel@nongnu.org; Fri, 28 Dec 2018 13:22:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gcwkI-0006zZ-Br for qemu-devel@nongnu.org; Fri, 28 Dec 2018 13:21:14 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42206) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gcw1j-0001Wc-G3 for qemu-devel@nongnu.org; Fri, 28 Dec 2018 12:34:30 -0500 From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Date: Fri, 28 Dec 2018 18:33:52 +0100 Message-Id: <20181228173356.15359-2-philmd@redhat.com> In-Reply-To: <20181228173356.15359-1-philmd@redhat.com> References: <20181228173356.15359-1-philmd@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PATCH v4 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: David Hildenbrand , Eric Blake , Juan Quintela , Paolo Bonzini , "Dr. David Alan Gilbert" , Igor Mammedov , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , David Gibson , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Markus Armbruster , "Michael S. Tsirkin" , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Thomas Huth 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 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): 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