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Mon, 03 May 2021 12:20:56 +0000 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-158-eNDpXcXQN7-pDpflGzOLyg-1; Mon, 03 May 2021 13:20:47 +0100 X-MC-Unique: eNDpXcXQN7-pDpflGzOLyg-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 3 May 2021 13:20:46 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.015; Mon, 3 May 2021 13:20:46 +0100 From: David Laight To: 'Arnd Bergmann' , Matthew Wilcox , Linus Torvalds , Segher Boessenkool , Joe Perches , Miguel Ojeda , Masahiro Yamada , Albert Ou , Linux Kbuild mailing list , Greg Kroah-Hartman , Jonathan Corbet , "Linux Doc Mailing List" , linux-kernel , Palmer Dabbelt , "Paul Walmsley" , Catalin Marinas , Miguel Ojeda , Paul Mackerras , linux-riscv , linuxppc-dev , Will Deacon , Linux ARM Subject: RE: [PATCH] Raise the minimum GCC version to 5.2 Thread-Topic: [PATCH] Raise the minimum GCC version to 5.2 Thread-Index: AQHXP/5biZEe8rdCR0StYtnq1hyuzarRqk5g Date: Mon, 3 May 2021 12:20:45 +0000 Message-ID: References: <20210501151538.145449-1-masahiroy@kernel.org> <3943bc020f6227c8801907317fc113aa13ad4bad.camel@perches.com> <20210502183030.GF10366@gate.crashing.org> <81a926a3bdb70debe3ae2b13655ea8d249fb9991.camel@perches.com> <20210502203253.GH10366@gate.crashing.org> <20210502223007.GZ1847222@casper.infradead.org> In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210503_052054_810952_D1F35F39 X-CRM114-Status: GOOD ( 19.72 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Arnd Bergmann > Sent: 03 May 2021 10:25 ... > One scenario that I've seen previously is where user space and > kernel are built together as a source based distribution (OE, buildroot, > openwrt, ...), and the compiler is picked to match the original sources > of the user space because that is best tested, but the same compiler > then gets used to build the kernel as well because that is the default > in the build environment. If you are building programs for release to customers who might be running then on old distributions then you need a system with the original userspace headers and almost certainly a similar vintage compiler. Never mind RHEL7 we have customers running RHEL6. (We've managed to get everyone off RHEL5.) So the build machine is running a 10+ year old distro. I did try to build on a newer system (only 5 years old) but the complete fubar of memcpy() makes it impossible to compile C programs that will run on an older libc. And don't even mention C++, the 'character traits' is just plain horrid - enough to make me want to remove every reference to CString from the small amount of C++ we have. To quote our makefile: # C++ is fighting back. # I'd like to be able to compile on a 'new' system and still be able to run # the binaries on RHEL 6 (2.6.32 kernel 2011 era libraries). # But even linking libstdc++ static still leaves # an undefined C++ symbol that the dynamic loader barfs on. # The static libstdc++ also references memcpy@GLIBC_2.14 - but that can be # 'solved' by adding an extra .so that defines the symbol (and calls memmove()). # I've also tried pulling a single .o out of libstc++.a. This might work if # the .o is small and self contained. # # For now we statically link libstc++ and continue to build on an old system. C++LDLIBS := -Wl,-Bstatic -lstdc++ -Wl,-Bdynamic It would be nice to be able to build current kernels (for local use) on the 'new' system - but gcc is already too old. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel