Date: Sun, 8 Oct 2017 22:01:13 -0700 From: Nathan Whitehorn <nwhitehorn@freebsd.org> To: freebsd-arch@freebsd.org Subject: Re: Making C++11 a hard requirement for FreeBSD Message-ID: <e1b1b84a-9f6f-d0d7-7e26-b3ef3cc35698@freebsd.org> In-Reply-To: <20171006072010.ygq3k5ygwxykk4nb@ivaldir.net> References: <CANCZdfq5=KRp4NYKsc15gyS9C7CxrBFxcKQLPwnb_0oPb15vJw@mail.gmail.com> <2116882.XEKuxOb729@ralph.baldwin.cx> <20171006072010.ygq3k5ygwxykk4nb@ivaldir.net>
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On 10/06/17 00:20, Baptiste Daroussin wrote: > On Thu, Oct 05, 2017 at 11:47:57PM +0000, John Baldwin wrote: >> On Thursday, October 05, 2017 04:28:44 PM Warner Losh wrote: >>> I'd like to start a conversation about the viability of making C++11 a hard >>> requirement for bootstrapping FreeBSD and setting a specific deadline for >>> doing so. >>> >>> This discussion is motivated by an ask from the jemalloc folks to use a >>> limited subset of C++11 inside of malloc in such a way that is C safe (so >>> the C programs wouldn't bloat with a C++ runtime). That's an ongoing >>> discussion in another forum, and isn't appropriate for this thread because >>> this has become a frequent request (but if you have opinions, please find >>> the thread in current@ about it). I don't know the timeline of their plans >>> to do this. >>> >>> I'd like to take the rather vague plans we've had "before 12" and create a >>> timeline for removal of gcc 4.2 coupled with a requirement for support in >>> clang or a working external toolchain. This requirement would be coupled >>> with the requirement that the external toolchain support C++11 constructs. >>> >>> I'd like to propose we do this 12/31/17. Any architectures that can't meet >>> this timeline will be disconnected from universe at that time and deleted >>> 3/31/18. >>> >>> It's my belief that i386, amd64, arm, aarch64, powerpc and powerpc64 are >>> ready for this change and mips* would be ready for this change with an >>> external clang toolchain. I'm unsure of riscv and sparc64, but suspect that >>> a newer version of gcc as an external toolchain could work. >> In-tree clang 5.0 for MIPS mostly works (modulo some small patches). However, >> it requires external ld.bfd. I know that there ld.lld can link a working >> mips64 world with some patches (notably the multigot patch). mips works fine >> with external GCC. riscv is already using external GCC that is C++11-capable. >> >> The problem with external GCC is that you can cross-build a world + kernel >> just fine and get a working system via CROSS_TOOLCHAIN=foo-gcc. However, >> that system has no viable '/usr/bin/cc' once GCC 4.2 is removed. bapt@ >> started on ports to cross-build binutils and gcc packages via the base/* >> ports, but those are not yet finished / fully tested. I don't think anyone >> has thought about how release builds will work either with only an external >> toolchain available. (I'm pretty sure sparc64 has booted fine with >> external GCC, it's just in the same boat as mips with regard to /usr/bin/cc.) > Actually I did test those and they were working (tested in qemu) they were > working fine. I have given up working on them due to the lack of interested by > the community (by interest I mean people really testing, working on it, not just > saying "hey nice sounds cool"). > > As for the boot when I initially worked on external toolchain sparc64 was my > guinea pig and so yes it worked an booted just fine. So far as I know, we never solved any of the infrastructural problems associated with this concept: 1. Providing built releases with a /usr/bin/cc 2. Coversioning base and in-ports toolchain, including ensuring commit atomicity between toolchains and libc 3. Adding a dependency on ports for src, including out-of-tree code that has to be fetched from external servers 4. Getting make universe to do the right thing We really need to solve those. If we go the external toolchain route, which it is not clear to me is the best option, #2 and #1 are quite complex problems. I think that, frankly, a deadline in two months to solve this set of political problems we have had for two years is probably crazy, but maybe making the status quo unsustainable will finally force progress. Also, are there any directions for how to build a toolchain from the base ports? I haven't been able to figure it out -- the README starts with "pkg install", but that doesn't get me very far on platforms without binary packages, which are the ones this is meant to target. -Nathan
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