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mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.onmicrosoft.com; s=selector2-citrix-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=OKlQwR57eOPgWtz7lCdOmogpzFIwemmD6XTnjE4GD3g=; b=CCMnsmHpssME2IjHY25QCeV3FzksqN89xxY1YhRNFPTjC21AJxJDN1rY2+7uIsUEDtz2JoTTYdjrV0EkDWRMJ7a7yeUOX6JG4fZz1Cvp6gz77WNkru6U6EzJfv/FV43PpWznl63U6O58heVOXxgqJ5BwDV1pR89cUn/GWqJrkc8= To: Lin Liu , CC: George Dunlap , Ian Jackson , Jan Beulich , Julien Grall , Stefano Stabellini , Wei Liu References: <89afdafa9020ab77b9d662bd5c8f7b2d31e53c5c.1634897942.git.lin.liu@citrix.com> From: Andrew Cooper Subject: Re: [PATCH v2 1/7] xen: implement byteswap.h Message-ID: Date: Fri, 22 Oct 2021 15:00:57 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 In-Reply-To: <89afdafa9020ab77b9d662bd5c8f7b2d31e53c5c.1634897942.git.lin.liu@citrix.com> Content-Type: text/plain; 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It needs to be #ifndef __has_builtin because otherwise a random GCC 10 build I have fails with: /local/security/xen.git/xen/include/xen/byteswap.h:6:19: error: missing binary operator before token "(" =C2=A0=C2=A0=C2=A0 6 | #if !__has_builtin(__builtin_bswap16) I suspect it was a build of GCC 10 before __has_builtin() support was added, but either way, we should be predicating on __has_builtin itself, not version guesswork. ~Andrew