<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On May 10, 2018, at 1:50 PM, Chandler Carruth <<a href="mailto:chandlerc@google.com" class="">chandlerc@google.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Last time this came up, there were a lot of people that were stuck on GCC 4.9 due to ABI reasons. I think forcing that upgrade is going to be the most disruptive part of this, and I think that will really need a decent amount of time. =[</div></div></blockquote><div><br class=""></div><div>Those people don’t build a browser? Because if they build any one of the 3 major ones they’re not using GCC 4.9 AFAICT.</div><div><br class=""></div><br class=""><blockquote type="cite" class=""><div class=""><div class="gmail_quote"><div dir="ltr" class="">On Thu, May 10, 2018 at 2:26 PM JF Bastien via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space" class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On May 10, 2018, at 12:25 PM, Evgeny Astigeevich via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank" class="">llvm-dev@lists.llvm.org</a>> wrote:</div><br class="m_1966951477189470441Apple-interchange-newline"><div class=""><div class="m_1966951477189470441WordSection1" style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Hi,<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class="">IMHO, it’s a good idea to move to C++14 first.<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class="">What do you think about doing this by two phases:<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Phase1: require GCC >= 5 but build in C++11 mode (this will give time to adapt build infrastructure to a new gcc)<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Phase2: switch to C++14</div></div></div></blockquote><div class=""><br class=""></div></div></div><div style="word-wrap:break-word;line-break:after-white-space" class=""><div class=""><div class="">Sounds reasonable, here’s a patch:</div><div class=""><div style="margin:0px;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;background-color:rgb(255,255,255)" class=""><span style="text-decoration:underline;font-variant-ligatures:no-common-ligatures" class=""><a href="https://reviews.llvm.org/D46723" target="_blank" class="">https://reviews.llvm.org/D46723</a></span></div><div style="margin:0px;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;background-color:rgb(255,255,255)" class=""><span style="text-decoration:underline;font-variant-ligatures:no-common-ligatures" class=""><br class=""></span></div></div></div></div><div style="word-wrap:break-word;line-break:after-white-space" class=""><div class=""><br class=""><blockquote type="cite" class=""><div class=""><div class="m_1966951477189470441WordSection1" style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Thanks,<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Evgeny<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div style="border-style:solid none none;border-top-width:1pt;border-top-color:rgb(181,196,223);padding:3pt 0cm 0cm" class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><b class=""><span style="font-size:12pt" class="">From:<span class="m_1966951477189470441Apple-converted-space"> </span></span></b><span style="font-size:12pt" class="">llvm-dev <<a href="mailto:llvm-dev-bounces@lists.llvm.org" style="color:purple;text-decoration:underline" target="_blank" class="">llvm-dev-bounces@lists.llvm.org</a>> on behalf of Reid Kleckner via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" style="color:purple;text-decoration:underline" target="_blank" class="">llvm-dev@lists.llvm.org</a>><br class=""><b class="">Reply-To:<span class="m_1966951477189470441Apple-converted-space"> </span></b>Reid Kleckner <<a href="mailto:rnk@google.com" style="color:purple;text-decoration:underline" target="_blank" class="">rnk@google.com</a>><br class=""><b class="">Date:<span class="m_1966951477189470441Apple-converted-space"> </span></b>Thursday, 10 May 2018 at 19:50<br class=""><b class="">To:<span class="m_1966951477189470441Apple-converted-space"> </span></b>Zachary Turner <<a href="mailto:zturner@google.com" style="color:purple;text-decoration:underline" target="_blank" class="">zturner@google.com</a>><br class=""><b class="">Cc:<span class="m_1966951477189470441Apple-converted-space"> </span></b>llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" style="color:purple;text-decoration:underline" target="_blank" class="">llvm-dev@lists.llvm.org</a>><br class=""><b class="">Subject:<span class="m_1966951477189470441Apple-converted-space"> </span></b>Re: [llvm-dev] Using C++14 code in LLVM<u class=""></u><u class=""></u></span></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">The easy way not to have a three year discussion is to not worry about it for another three years. :)<u class=""></u><u class=""></u></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">So, I think we should take the easy things on the table and just move to C++14 in the near future. It's just a matter of dropping support for building on distros that only have GCC <5 (aka Trusty, which is from 2014 itself). Let's do that and call it a day.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">---<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Aside: I'm always kind of amused by talk of moving to the next "standard version" when the reality is that every C++ project is always held back by the compilers and standard libraries that they actually use in practice. We say LLVM requires C++11 which mandates a working set of threading primitives, but in practice those don't exist on some platforms that people would like us to support, so we end up maintaining the LLVM_ENABLE_THREADING=0 build for them.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">It seems more practical to simply list the minimum versions of supported toolchains that are commonly used to build, i.e. GCC 5, MSVC 2015, Clang 3.N, libc++ 3.N, libstdc++ 3.N, etc.<u class=""></u><u class=""></u></div></div></div><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">On Thu, May 10, 2018 at 11:36 AM Zachary Turner via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" style="color:purple;text-decoration:underline" target="_blank" class="">llvm-dev@lists.llvm.org</a>> wrote:<u class=""></u><u class=""></u></div></div><blockquote style="border-style:none none none solid;border-left-width:1pt;border-left-color:rgb(204,204,204);padding:0cm 0cm 0cm 6pt;margin-left:4.8pt;margin-right:0cm" type="cite" class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">If it's the only thing we can agree then I'll take it, but I just worry that 3 years from now we're going to start another 3 year discussion, so that any actual move to C++17 would end up taking double the time.<u class=""></u><u class=""></u></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Are the issues specific to C++17 additions to the standard library? What if you allow C++17 language features but not C++17 library features? I'm guessing this is too simple though and isn't sufficient to avoid the problems (which I don't know anything about, so you'll have to enlighten me)?<u class=""></u><u class=""></u></div></div></div><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">On Thu, May 10, 2018 at 11:28 AM JF Bastien <<a href="mailto:jfbastien@apple.com" style="color:purple;text-decoration:underline" target="_blank" class="">jfbastien@apple.com</a>> wrote:<u class=""></u><u class=""></u></div></div><blockquote style="border-style:none none none solid;border-left-width:1pt;border-left-color:rgb(204,204,204);padding:0cm 0cm 0cm 6pt;margin-left:4.8pt;margin-right:0cm" type="cite" class=""><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><br class=""><br class=""><u class=""></u><u class=""></u></div><blockquote style="margin-top:5pt;margin-bottom:5pt" type="cite" class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">On May 10, 2018, at 11:22 AM, Zachary Turner <<a href="mailto:zturner@google.com" style="color:purple;text-decoration:underline" target="_blank" class="">zturner@google.com</a>> wrote:<u class=""></u><u class=""></u></div></div><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Windows has never been the issue. Honestly, MSVC on Windows is "fully C++17 conformant" [1].<u class=""></u><u class=""></u></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">The issue has and always will be GCC. Given that a bump in any version of GCC has been (and will remain) difficult for some time, I propose that we skip C++14 and move to 17. We don't want to have a multi-year disccusion about this again any time soon, and from what I gather, nobody has any more reservations about moving to C++17 than they do about moving to C++14. They only have reservations about moving to anything at all. So if we're gonna move, we should go all the way.<u class=""></u><u class=""></u></div></div></div></div></blockquote><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div></div></div><div class=""><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">WebKit’s move to C++17 hasn’t been super smooth because of GCC / libstdc++ issues in both GCC 6 and GCC 7. It’s all fixable, but given LLVM's slow move out of C++11 I’d rather get C++14 now rather than a painful transition to C++17 that drags on as we discover issues.<u class=""></u><u class=""></u></div></div></div></div><div class=""><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><br class=""><br class=""><u class=""></u><u class=""></u></div><blockquote style="margin-top:5pt;margin-bottom:5pt" type="cite" class=""><div class=""><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Just my 2c.<u class=""></u><u class=""></u></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">[1]<span class="m_1966951477189470441Apple-converted-space"> </span><a href="https://blogs.msdn.microsoft.com/vcblog/2018/05/07/announcing-msvc-conforms-to-the-c-standard/" style="color:purple;text-decoration:underline" target="_blank" class="">https://blogs.msdn.microsoft.com/vcblog/2018/05/07/announcing-msvc-conforms-to-the-c-standard/</a><u class=""></u><u class=""></u></div></div></div></div><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">On Thu, May 10, 2018 at 11:18 AM Eric Christopher <<a href="mailto:echristo@gmail.com" style="color:purple;text-decoration:underline" target="_blank" class="">echristo@gmail.com</a>> wrote:<u class=""></u><u class=""></u></div></div><blockquote style="border-style:none none none solid;border-left-width:1pt;border-left-color:rgb(204,204,204);padding:0cm 0cm 0cm 6pt;margin-left:4.8pt;margin-right:0cm" type="cite" class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Once again, I'm totally down for this and think we should do it. I worry about windows, but ...<u class=""></u><u class=""></u></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Zach: How's windows c++14 support looking?<u class=""></u><u class=""></u></div></div></div><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">-eric<u class=""></u><u class=""></u></div></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">On Thu, May 10, 2018 at 10:01 AM JF Bastien via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" style="color:purple;text-decoration:underline" target="_blank" class="">llvm-dev@lists.llvm.org</a>> wrote:<u class=""></u><u class=""></u></div></div><blockquote style="border-style:none none none solid;border-left-width:1pt;border-left-color:rgb(204,204,204);padding:0cm 0cm 0cm 6pt;margin-left:4.8pt;margin-right:0cm" type="cite" class=""><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Hi folks!<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Six more months have come and gone, and maybe we could move LLVM to C++14 now?<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">The issues I picked out from the last discussion:<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 72pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><span class="">1.<span style="font-style:normal;font-variant-caps:normal;font-weight:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"" class=""> <span class="m_1966951477189470441Apple-converted-space"> </span></span></span>Some folks want an official policy about compiler support before updating the standard version we use.<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt 72pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><span class="">2.<span style="font-style:normal;font-variant-caps:normal;font-weight:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"" class=""> <span class="m_1966951477189470441Apple-converted-space"> </span></span></span>Worries about which GCC version is available in which distro.<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt 72pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><span class="">3.<span style="font-style:normal;font-variant-caps:normal;font-weight:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"" class=""> <span class="m_1966951477189470441Apple-converted-space"> </span></span></span>Worries about MSVC.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Instead of rehashing the compiler per distro surveys from previous discussion, and instead of talking bootstrap, let me offer three data points:<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 72pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><span style="font-size:10pt;font-family:Symbol" class=""><span class="">·<span style="font-style:normal;font-variant-caps:normal;font-weight:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"" class=""> <span class="m_1966951477189470441Apple-converted-space"> </span></span></span></span>WebKit is <a href="https://lists.webkit.org/pipermail/webkit-dev/2018-March/029922.html" style="color:purple;text-decoration:underline" target="_blank" class="">moving to C++17</a> (from C++14) right now †<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt 72pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><span style="font-size:10pt;font-family:Symbol" class=""><span class="">·<span style="font-style:normal;font-variant-caps:normal;font-weight:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"" class=""> <span class="m_1966951477189470441Apple-converted-space"> </span></span></span></span>Chromium <a href="https://groups.google.com/a/chromium.org/d/msg/cxx/ow7hmdDm4yw/eV6KWL2yAQAJ" style="color:purple;text-decoration:underline" target="_blank" class="">started moving to C++14</a> in August of last year<u class=""></u><u class=""></u></div><div style="margin:0cm 0cm 0.0001pt 72pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><span style="font-size:10pt;font-family:Symbol" class=""><span class="">·<span style="font-style:normal;font-variant-caps:normal;font-weight:normal;font-stretch:normal;font-size:7pt;line-height:normal;font-family:"Times New Roman"" class=""> <span class="m_1966951477189470441Apple-converted-space"> </span></span></span></span>Firefox uses <a href="https://developer.mozilla.org/en-US/docs/Mozilla/Using_CXX_in_Mozilla_code" style="color:purple;text-decoration:underline" target="_blank" class="">some C++14</a><u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">What I get from this data: if your distro bundles a modern web browser, it already builds some C++14,<span class="m_1966951477189470441Apple-converted-space"> </span><i class="">somehow</i>.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">The LLVM community has been talking about this for a while now, and I’m not aware of a policy coming to light. I don’t think we need a policy given the above data. So how about we… just kinda... move LLVM to C++14?<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">Thanks!<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">JF<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">† the move to C++17 is very painful, but 14 has been working great in WebKit for quite a long time.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class=""><u class=""></u> <u class=""></u></div></div><div class=""><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Last time we discussed this, the consensus was "I think we can survive<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> another year without generalized constexpr and variable templates".<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Well, we did indeed survive. And it's been exactly a year! So naturally,<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> it only makes sense to revive this :)<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> There's an active conversation going on in IRC right now, and it seems like<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> there is more desire than there was last year.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> What are the main gains from allowing C++14?<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * Variable templates<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * Generalized constexpr<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * Return-type Deduction<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * Generic Lambdas<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * std::make_unique<> (the source of many build bot breakages)<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> What are the main gains from allowing C++17? [1]<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * [[nodiscard]] attribute<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * structured bindings<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * constexpr-if<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * guaranteed copy elision<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * numerous new library types: optional, string_view, variant, byte,<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * numerous new algorithms: parallel algorithms, too many to list<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * Probably some more, but I just tried to hit the biggest ones.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> First, it seems like if we want to enable C++14 we need GCC >= 5.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> And if we want to enable C++17 we need GCC >= 7.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> With that out of the way, here were some of the issues that were raised<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> last time:<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Issue: Ubuntu 14.04 LTS is on GCC 4.8.x, and we have to support it until<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> end of life.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Resolution: LTS is right around the corner, in 6 more months.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Issue: Various other platforms have older GCCs as their system compiler,<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> and it's annoying to upgrade.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Question: Do any of these not have a port you can install? For example,<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> NetBSD 7 appears to have GCC 5.3 as a port, if DistroWatch is any<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> indication. It could be wrong though and I could also be misinterpreting<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> it.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Issue: If we're going to make people bootstrap a compiler, we might as well<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> go all the way to C++17.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Comment: I'm not opposed.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Some questions / comments of my own:<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * Where is this policy about Ubuntu and LTS documented? Does this mean,<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> for example, that we will not be able to use C++17 until 2023 (16.04 LTS<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> has only GCC 5.3.1)? That seems a bit unreasonable. And there's no<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> guarantee that 18.04 LTS will even have GCC 7 or higher either, so it could<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> be 2025 or 2027.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * We've asked people in the past to build a modern toolchain. For example,<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> we did it with C++11 and Ubuntu 12.04 LTS. Is C++17 compelling enough to<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> justify this again?<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * GCC 4.9 probably isn't sufficient to justify an increase for anyone, as<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> it lacks two of the more sought-after features of C++14 (variable templates<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> and generalized constexpr). So IMO we should require a bump to GCC 5 or<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> higher, or not at all.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * Clang 6 supports all of C++20, and it builds with only C++11, so we<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> shouldn't have to worry too much about the problem of needing to "daisy<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> chain" compilers to finally get the latest version of LLVM building. "GCC<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> 4.8 -> Clang 6 - > Clang ToT" should hold up through C++1z.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> * While we obviously can't be tied to the versioning of every single distro<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> out there, some are "bigger" than others. Which are big enough that<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> warrant serious consideration? The ones I found are (and I did my best to<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> aggregate all this, but please correct me if anything is incorrect or<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> misrepresented):<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> OpenBSD - Ships with GCC 4.2.1 anyway. They are already having to<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> bootstrap something, so the proposal here does not change anything, because<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> even current LLVM doesn't compile with GCC 4.2.1<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> CentOS & RHEL - No version of Distro, including trunk, has GCC >= 4.8.5<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> (are there ports?)<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Debian - Minimum version 9 for GCC >= 5 (are there ports for earlier<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> releases?)<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Fedora - Minimum version 24 for GCC >= 5, minimum version 26 for GCC >= 7<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> Ubuntu - Minimum LTS 16.04 for GCC >= 5<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> NetBSD - Version 7 has GCC 4.8.4 by default, but contains port for 5.3.0<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> FreeBSD - Minimum Version 11 for GCC >= 5<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> So, thoughts?<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> [1] - Note that we'd need to wait a few more revs for MSVC before allowing<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> C++17, but given that it's becoming easier and easier to bump the minimum<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> MSVC version, I'm discounting this as a factor, as MSVC will not really be<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> the bottleneck in any real sense.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> On Tue, Oct 4, 2016 at 2:15 PM Mehdi Amini <mehdi.amini at<span class="m_1966951477189470441Apple-converted-space"> </span><a href="http://apple.com/" style="color:purple;text-decoration:underline" target="_blank" class="">apple.com</a>> wrote:<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">> <u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> On Oct 4, 2016, at 2:10 PM, Reid Kleckner <rnk at<span class="m_1966951477189470441Apple-converted-space"> </span><a href="http://google.com/" style="color:purple;text-decoration:underline" target="_blank" class="">google.com</a>> wrote:<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> On Tue, Oct 4, 2016 at 11:58 AM, Mehdi Amini <mehdi.amini at<span class="m_1966951477189470441Apple-converted-space"> </span><a href="http://apple.com/" style="color:purple;text-decoration:underline" target="_blank" class="">apple.com</a>><u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> wrote:<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> On Oct 4, 2016, at 8:40 AM, Reid Kleckner via llvm-dev <<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> llvm-dev at<span class="m_1966951477189470441Apple-converted-space"> </span><a href="http://lists.llvm.org/" style="color:purple;text-decoration:underline" target="_blank" class="">lists.llvm.org</a>> wrote:<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> On Tue, Oct 4, 2016 at 8:29 AM, Zachary Turner <zturner at<span class="m_1966951477189470441Apple-converted-space"> </span><a href="http://google.com/" style="color:purple;text-decoration:underline" target="_blank" class="">google.com</a>><u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> wrote:<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>>> I ask because many of these LTS distros are notoriously slow at updating<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>>> their packages. While some people may think C++14 doesn't provide enough<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>>> bang for the buck to justify bumping to GCC 4.9, C++17 definitely does. But<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>>> at that point we're going to be talking about GCC 6.1 or 6.2, which is<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>>> going to be significantly harder unless we want to wait 5-7 years, and I<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>>> suspect people won't.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> If by "notoriously slow" you mean they don't bump their toolchain<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> versions at all, then yeah. We just wait until the LTS release is at<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> end-of-life before dropping it.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> That’s the first time I read about this policy: we support every linux<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> LTS distribution till their end-of-life? Only Ubuntu? Do you have a pointer<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> where it is documented / discussed?<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>> (Note that Ubuntu LTS is 5 years AFAIK.)<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> Sorry, I didn't mean to refer to the LTS support lifetime. I just meant we<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> support the last LTS until we can reasonably expect users to have upgraded<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> to the new one. If there's an LTS release every two years, then we want to<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> keep supporting them for at least three years to give people a year to<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> upgrade.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> OK, got it.<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> Thanks for clarifying!<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>> Mehdi<u class=""></u><u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div><div class=""><div style="margin:0cm 0cm 0.0001pt 36pt;font-size:11pt;font-family:Calibri,sans-serif" class="">>><u class=""></u> <u class=""></u></div></div></div></div><div style="margin:0cm 0cm 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