From mint-bounce@lists.fishpool.fi Tue Jan 22 17:29:10 2008 X-Original-To: fnaumann@mail.boerde.de Delivered-To: fnaumann@mail.boerde.de Message-ID: <4749F7DC.6050708@highlandsun.com> Date: Sun, 25 Nov 2007 14:31:56 -0800 From: Howard Chu User-Agent: Mozilla/5.0 (X11; U; Linux i686; rv:1.9b2pre) Gecko/2007111122 SeaMonkey/2.0a1pre MIME-Version: 1.0 To: Thomas Huth Cc: =?UTF-8?B?VmluY2VudCBSaXZpw6hyZQ==?= , emutos-devel@lists.sourceforge.net, mint@fishpool.com Subject: Re: [MiNT] [Emutos-devel] Emutos and gcc-4.2.2 References: <4745708C.5010104@users.sourceforge.net> <20071123005939.11adea43@phineus> <47476378.1080906@users.sourceforge.net> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed X-MIME-Autoconverted: from 8bit to quoted-printable by highlandsun.propagation.net id lAPMYDum003161 X-ecartis-version: Ecartis v1.0.0 Sender: mint-bounce@lists.fishpool.fi Errors-To: mint-bounce@lists.fishpool.fi X-original-sender: hyc@highlandsun.com Precedence: bulk List-help: List-unsubscribe: List-Id: X-List-ID: List-subscribe: List-owner: List-post: X-Virus-Scanned: by amavisd-new at relay.boerde.de X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on relay.boerde.de X-Spam-Status: No, hits=-1.0 tagged_above=-50.5 required=7.0 tests=BAYES_00 X-Spam-Level: Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by freemint id m0MGP1at004618 Status: X-Status: X-Keywords: Thomas Huth wrote: > Hi! > > On Nov 24, 2007 12:34 AM, Vincent Rivière > wrote: >> I would like to speak about another "feature" : alignment. >> >> By default, GCC aligns structure members on 4-byte boundaries, producing >> useless 2-byte holes in a structure where longs and shorts are mixed. I >> patched it long ago to use a 2-byte default alignment, so no space is >> wasted. Some people said that the 68020+ CPU have faster memory access >> to longs aligned on 32-bit boundaries. Is it true on Atari computers ? Yes, on Atari TT and Falcon030. It's true for any system with 68020+, which all have 32 bit data buses. > I've heard that, too, but I am not an expert here ... that's maybe a > better question to the MiNT developers since they are more likely > working on 68030 machines than the folks here on the EmuTOS mailing > list. >> I recently discovered another "feature" of GCC. When function arguments >> are pushed on the stack, they are aligned on an "int" boundary. When >> compiling with -mshort, there is no additional filler. But when -mshort >> is not used, pushing a short then a long causes the long to be aligned 2 >> bytes further. A short filler is inserted between the 2 values. Just >> like structure alignment, it seems to me that such alignment is useless >> on the Atari platform. I plan to remove this alignment in my next build. Bad idea. > > Well, I think the default size of items that are pushed on the stack > should be sizeof(int). > For example when you have declared following function in one file: > > int myfunc(int a, int b) > { > return a + b; > } > > And in another file you call myfunc(3, 5), but there is no prototype > for myfunc before... > ... this is perfectly valid C (despite it's ugly due to the missing > prototype), but it will fail as soon as you disable this "filler" > values on the stack. I think it's better not to disable these > "fillers". Right. -- -- Howard Chu Chief Architect, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/