<div dir="ltr"><div>Libc++ is a C++11 STL implementation that tolerates C++03 compilers.</div><div>If a feature can be reasonably implemented in C++03, then we provide it.</div><div><atomic> is one example, <thread>, <unordered_map> and `std::shared_ptr` are others.</div><div><br></div><div>All of these components should have tests that run in C++03 (Tests are disabled in C++03 using the comment // UNSUPPORTED: c++98, c++03).</div><div><br></div><div><br></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Feb 6, 2019 at 11:39 PM Olivier Giroux via libcxx-dev <<a href="mailto:libcxx-dev@lists.llvm.org">libcxx-dev@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal">Maybe another way to test these waters is to ask what is actually being _<i>tested_</i>?<u></u><u></u></p>
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<p class="MsoNormal">Olivier<u></u><u></u></p>
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<p class="MsoNormal"><b><span style="font-size:12pt;color:black">From: </span></b><span style="font-size:12pt;color:black"><<a href="mailto:jfbastien@apple.com" target="_blank">jfbastien@apple.com</a>> on behalf of JF Bastien <<a href="mailto:jfbastien@apple.com" target="_blank">jfbastien@apple.com</a>><br>
<b>Date: </b>Wednesday, February 6, 2019 at 11:21 AM<br>
<b>To: </b>Olivier Giroux <<a href="mailto:OGiroux@nvidia.com" target="_blank">OGiroux@nvidia.com</a>><br>
<b>Cc: </b>"<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank">libcxx-dev@lists.llvm.org</a>" <<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank">libcxx-dev@lists.llvm.org</a>><br>
<b>Subject: </b>Re: [libcxx-dev] What C++03 support should <atomic> have?<u></u><u></u></span></p>
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<p class="MsoNormal">Doing atomics before 11 was pretty wild… So I understand that people using an old C++ want some nice atomics. At the same time… They really should update to C++11 or later.
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<p class="MsoNormal">What does libc++ try to do with new library features on old languages? Seems easy enough so support most of say optional or variant (without CTAD) before C++17. Is this done consistently? And how far back, do we even try to support C++98?
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<p class="MsoNormal">It seems like we can be nice where it’s easy, but at some point in time are we just supporting stuff nobody cares about?<u></u><u></u></p>
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<p class="MsoNormal">On Feb 5, 2019, at 9:33 PM, Olivier Giroux via libcxx-dev <<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank">libcxx-dev@lists.llvm.org</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal">Sorry, that quote is from my patch, but there’s identical code elsewhere in the file. I swear!<span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal"> <span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal">Olivier<span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal"><b><span style="font-size:12pt">From:<span class="gmail-m_-2222480216075481894apple-converted-space"> </span></span></b><span style="font-size:12pt">libcxx-dev <<a href="mailto:libcxx-dev-bounces@lists.llvm.org" target="_blank">libcxx-dev-bounces@lists.llvm.org</a>> on behalf
of Olivier Giroux via libcxx-dev <<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank">libcxx-dev@lists.llvm.org</a>><br>
<b>Reply-To:<span class="gmail-m_-2222480216075481894apple-converted-space"> </span></b>Olivier Giroux <<a href="mailto:OGiroux@nvidia.com" target="_blank">OGiroux@nvidia.com</a>><br>
<b>Date:<span class="gmail-m_-2222480216075481894apple-converted-space"> </span></b>Tuesday, February 5, 2019 at 9:33 PM<br>
<b>To:<span class="gmail-m_-2222480216075481894apple-converted-space"> </span></b>"<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank">libcxx-dev@lists.llvm.org</a>" <<a href="mailto:libcxx-dev@lists.llvm.org" target="_blank">libcxx-dev@lists.llvm.org</a>><br>
<b>Subject:<span class="gmail-m_-2222480216075481894apple-converted-space"> </span></b>[libcxx-dev] What C++03 support should <atomic> have?<u></u><u></u></span></p>
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<p class="MsoNormal">There is a little bit of code in this file that suggests it once worked in C++03.<span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal"> <span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal">Like so:<span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal" style="line-height:13.5pt;background:rgb(30,30,30)"><span style="font-size:10pt;font-family:Consolas;color:rgb(197,134,192)">#ifndef</span><span class="gmail-m_-2222480216075481894apple-converted-space"><span style="font-size:10pt;font-family:Consolas;color:rgb(86,156,214)"> </span></span><span style="font-size:10pt;font-family:Consolas;color:rgb(220,220,170)">_LIBCPP_CXX03_LANG</span><span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal" style="line-height:13.5pt;background:rgb(30,30,30)"><span style="font-size:10pt;font-family:Consolas;color:rgb(212,212,212)"> <span class="gmail-m_-2222480216075481894apple-converted-space"> </span></span><span style="font-size:10pt;font-family:Consolas;color:rgb(220,220,170)">__cxx_atomic_type</span><span style="font-size:10pt;font-family:Consolas;color:rgb(212,212,212)">()
_NOEXCEPT =<span class="gmail-m_-2222480216075481894apple-converted-space"> </span></span><span style="font-size:10pt;font-family:Consolas;color:rgb(197,134,192)">default</span><span style="font-size:10pt;font-family:Consolas;color:rgb(212,212,212)">;</span><span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal" style="line-height:13.5pt;background:rgb(30,30,30)"><span style="font-size:10pt;font-family:Consolas;color:rgb(197,134,192)">#else</span><span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal" style="line-height:13.5pt;background:rgb(30,30,30)"><span style="font-size:10pt;font-family:Consolas;color:rgb(212,212,212)"> <span class="gmail-m_-2222480216075481894apple-converted-space"> </span></span><span style="font-size:10pt;font-family:Consolas;color:rgb(220,220,170)">__cxx_atomic_type</span><span style="font-size:10pt;font-family:Consolas;color:rgb(212,212,212)">()
_NOEXCEPT :<span class="gmail-m_-2222480216075481894apple-converted-space"> </span></span><span style="font-size:10pt;font-family:Consolas;color:rgb(220,220,170)">__a_value</span><span style="font-size:10pt;font-family:Consolas;color:rgb(212,212,212)">() {}</span><span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal" style="line-height:13.5pt;background:rgb(30,30,30)"><span style="font-size:10pt;font-family:Consolas;color:rgb(197,134,192)">#endif</span><span class="gmail-m_-2222480216075481894apple-converted-space"><span style="font-size:10pt;font-family:Consolas;color:rgb(212,212,212)"> </span></span><span style="font-size:10pt;font-family:Consolas;color:rgb(106,153,85)">//
_LIBCPP_CXX03_LANG</span><span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal">Is that an actual design goal? It looks like it’s broken right now.<span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal">Do we maintain this, or do we bump the assumed default to C++11?<span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal">Thanks for your guidance,<span style="font-size:12pt"><u></u><u></u></span></p>
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<p class="MsoNormal">Olivier<span style="font-size:12pt"><u></u><u></u></span></p>
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