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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW " title="NEW --- - std::char_traits<char16_t>::eof() returns valid code unit" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D24342&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=tajEgRSXaFZYv2dPoXZ5k2sijdreTFFFmGK007kdt2Y&s=KuQyNbrs0HZHEGfldpC35sbYTflN0UzWx1t3yRmygR4&e=">24342</a>
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<th>Summary</th>
<td>std::char_traits<char16_t>::eof() returns valid code unit
</td>
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<th>Product</th>
<td>libc++
</td>
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<th>Version</th>
<td>3.6
</td>
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<th>Hardware</th>
<td>Macintosh
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>All Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>david_work@me.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu, mclow.lists@gmail.com
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>[char.traits.specializations.char16_t] ยง21.2.3.2/3 says,
"The member eof() shall return an implementation-defined constant that cannot
appear as a valid UTF-16 code unit."
In libc++ it returns 0xDFFF, which is a valid second half of a surrogate pair.
Surrogate pairs are only needed outside the basic multilingual plane, so it
won't often be seen, but characters like U+123FF are valid and encoded by
0xDFFF.
On the other hand, U+FFFF is a "noncharacter," "intended for process-internal
uses" similarly to the byte order mark (which happens to be the preceding code
point U+FFFE). (<a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__unicode.org_charts_PDF_UFFF0.pdf&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=tajEgRSXaFZYv2dPoXZ5k2sijdreTFFFmGK007kdt2Y&s=-TNs9LrIxBuXhlcH18XWXvsg6OHuTFRSdL4LNaaYzbw&e=">http://unicode.org/charts/PDF/UFFF0.pdf</a>) U+FFFF is used by most
other environments, it is the value under libstdc++, and it coincides with WEOF
when wchar_t is UTF-16.</pre>
</div>
</p>
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