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<p class="MsoNormal">One thing I’ve since discovered is that clang doesn’t produce the leading * for anonymous namespace types either, so that would be the other half of such a change. See
<a href="https://llvm.org/PR34907">https://llvm.org/PR34907</a><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Louis Dionne <ldionne@apple.com><br>
<b>Date: </b>Thursday, May 14, 2020 at 5:59 AM<br>
<b>To: </b>Shoaib Meenai <smeenai@fb.com>, Eric Fiselier <ericwf@google.com><br>
<b>Cc: </b>"libcxx-dev@lists.llvm.org" <libcxx-dev@lists.llvm.org><br>
<b>Subject: </b>Re: [libcxx-dev] Non-merged type info name comparison<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in">Revisiting this, I think it would make sense to do that. The three modes would become:
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<p class="MsoNormal" style="margin-left:.5in">1) Unique: Assume RTTI is de-duplicated, and only ever compare pointers -- AS-IS TODAY<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">2) NonUnique: Assume RTTI is not de-deduplicated: compare pointers first, fall back to string comparison but not when it starts with * -- THIS IS DIFFERENT FROM TODAY<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">3) NonUniqueARMRTTIBit: Weird implementation for ARM64 -- DOESN'T CHANGE<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Eric, what do you think? It would be straightforward to implement, and it would unbreak the NonUnique variant in the cases where we have identically named types in anonymous namespaces -- an arguable bug in the
NonUnique implementation today.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Louis<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">On Sep 23, 2019, at 15:02, Shoaib Meenai via libcxx-dev <<a href="mailto:libcxx-dev@lists.llvm.org">libcxx-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">In<span class="apple-converted-space"> </span><a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_rL361913&d=DwMFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=_CncFX8flnXZAyUtjXRdGlfdWLjd9ENI8NmtbZ8khig&s=-niuKHWY_4JqFnEcc6SCTpTACfoEyMqpi3uzzAshu3E&e="><span style="color:#954F72">https://reviews.llvm.org/rL361913</span></a>,
libc++ gained the option to make type info comparisons use a strcmp on the type info name, which is useful for when we can’t guarantee RTTI uniqueness. I believe libstdc++ also defaults to strcmp comparisons. However, libstdc++ doesn’t perform the string comparison
when the type info name begins with the * character [1], which is the case for e.g. types defined in anonymous namespaces. Should libc++’s implementation be changed to match, at least when targeting Linux?<span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in">[1]<span class="apple-converted-space"> </span><a href="https://github.com/gcc-mirror/gcc/blob/277b02e227df91c686e7f7ad1ae21cd898611ca8/libstdc%2B%2B-v3/libsupc%2B%2B/typeinfo#L123"><span style="color:#954F72">https://github.com/gcc-mirror/gcc/blob/277b02e227df91c686e7f7ad1ae21cd898611ca8/libstdc%2B%2B-v3/libsupc%2B%2B/typeinfo#L123</span></a><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:9.0pt;font-family:Helvetica">_______________________________________________<br>
libcxx-dev mailing list<br>
</span><a href="mailto:libcxx-dev@lists.llvm.org"><span style="font-size:9.0pt;font-family:Helvetica;color:#954F72">libcxx-dev@lists.llvm.org</span></a><span style="font-size:9.0pt;font-family:Helvetica"><br>
</span><a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.llvm.org_cgi-2Dbin_mailman_listinfo_libcxx-2Ddev&d=DwMFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=_CncFX8flnXZAyUtjXRdGlfdWLjd9ENI8NmtbZ8khig&s=0QB244cb5snVBKHVYeKGL9YBf8YbYvHTZh2x86EKhXQ&e="><span style="font-size:9.0pt;font-family:Helvetica;color:#954F72">https://lists.llvm.org/cgi-bin/mailman/listinfo/libcxx-dev</span></a><o:p></o:p></p>
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