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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">However, 6/5 means we would not be moving ahead to full C++17 until 2024. Can you hold back the tidal wave of developer angst that long?
</span><span style="font-size:11.0pt;font-family:Wingdings;color:#1F497D">J</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Retrospectively, that policy means we would only now be starting the transition period to MSVC 2013, which wouldn't even enable C++11 IIRC. But MSVC is not
closely tied to distros the way gcc is, so applying the same policy there might not be appropriate.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></a></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> llvm-dev [mailto:llvm-dev-bounces@lists.llvm.org]
<b>On Behalf Of </b>Keane, Erich via llvm-dev<br>
<b>Sent:</b> Friday, May 11, 2018 12:05 PM<br>
<b>To:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> Re: [llvm-dev] A Short Policy Proposal Regarding Host Compilers<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Based on my reading of the release pages (<a href="https://gcc.gnu.org/releases.html">https://gcc.gnu.org/releases.html</a> and
<a href="http://releases.llvm.org/">http://releases.llvm.org/</a>)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">6/5 would make GCC 4.7 and Clang 3.1 required, and GCC 4.8 and Clang 3.3 the first to not warn.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">6/5 is surprisingly close to making the policy conform to exactly our current time-lag, where we are GCC4.8 (instead of 4.7) and Clang 3.1 (also 3.1).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Erich<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> Andrew Kelley [mailto:superjoe30@gmail.com]
<br>
<b>Sent:</b> Friday, May 11, 2018 8:58 AM<br>
<b>To:</b> Keane, Erich <erich.keane@intel.com><br>
<b>Cc:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> Re: [llvm-dev] A Short Policy Proposal Regarding Host Compilers<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I second this proposal, and I make a motion to lengthen 3/1.5 to 6/5.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Fri, May 11, 2018 at 9:37 AM, Keane, Erich via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Hi All-<br>
As we all know, the C++14 discussion is flaring up again. Chandler brought up that he would like a concrete plan to switch. In my opinion, this is insufficient, as it will result in us simply having this discussion AGAIN next release. Instead, I would prefer
us to have a concrete Policy on our host compilers. That way, changes like this are unsurprising to our users, and advance our codebase sufficiently. I believe the arguments for/against upgrading have been made repeatedly, so I won't repeat them here. My
proposal is thus:<br>
<br>
Starting with the Clang 7.0 release, we will officially support any major release of our host compilers (MSVC, GCC, Clang, ?ICC?) released in the past 3* years from our previous branch date to give trunk-developers time to transition (so for 7.0, 3 years before
January 3, 2018). This will be enforced via the CMake CheckCompilerVersion script (ala
<a href="https://reviews.llvm.org/D46723" target="_blank">https://reviews.llvm.org/D46723</a>). ADDITIONALLY, a CMake warning will be issued for any major release less than 1.5* years old to give our users sufficient time to transition/upgrade their compilers.
Finally, our dependent C++ version will be the best released standard officially supported by the collection of compilers (for example, we'd support -C++20 if all compilers had std=c++20 or eqiv, but NOT std=c++2a).
<br>
<br>
The 3-years/1.5 years would result in our minimum GCC/Clang becoming: GCC5.1/Clang3.6. We would WARN on anything older than GCC7.1/Clang3.8<br>
<br>
/End Proposal<br>
<br>
<br>
*: To Be Bikeshed<br>
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