From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chen Gang Subject: Re: [PATCH linux-next] net: batman-adv: use "__packed __aligned(2)" for each structure instead of "__packed(2)" region Date: Sun, 19 Jan 2014 17:51:25 +0800 Message-ID: <52DBA01D.6040000@gmail.com> References: <52DA65F4.5070501@gmail.com> <52DA7B9E.4040202@meshcoding.com> <4915262.qEFumRrH4p@radagast> <52DB9B39.9090502@meshcoding.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: James Hogan , David Miller , mareklindner@neomailbox.ch, sw@simonwunderlich.de, b.a.t.m.a.n@lists.open-mesh.org, netdev , "linux-kernel@vger.kernel.org" , linux-metag@vger.kernel.org, Dan Carpenter , Greg KH To: Antonio Quartulli Return-path: In-Reply-To: <52DB9B39.9090502@meshcoding.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 01/19/2014 05:30 PM, Antonio Quartulli wrote: > On 19/01/14 02:10, James Hogan wrote: >> >> It appears that the following gcc patch adds support for #pragma pack: >> http://gcc.gnu.org/ml/gcc-patches/2006-10/msg01115.html >> >> I gave it a quick spin on metag gcc (which is unfortunately stuck on an old >> version) and it seems to fix my simple test case so that #pragma pack(2) >> becomes equivalent to __packed __aligned(2) (for sizeof and __alignof__). >> > > Then I personally think that it is better to fix metag gcc instead of > changing the kernel. > > Actually there are many different spots where "#pragma pack" is used. > batman-adv is just the only one having compile time checks for structure > sizes. > What Antonio said sounds reasonable to me. >> >> However, the __packed and __aligned are linux specific macros to abstract >> compiler details, whereas #pragma pack appears to be a compiler-specific WIN32 >> style equivalent to GCC's __attribute__((packed)) and >> __attribute__((aligned(2))) (these are what __packed and __aligned use in >> compiler-gcc.h). >> >> Therefore I believe using the Linux abstractions is still more correct here. > > If you really think so, I'd suggest to grep in the kernel and catch all > the other occurrences of "#pragma pack" and change them all (assuming > that using __attribute__((aligned(2))) is the way to go). > Thanks. -- Chen Gang Open, share and attitude like air, water and life which God blessed