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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - basic_string does not respect NullablePointer requirements of the allocator's pointer"
href="http://llvm.org/bugs/show_bug.cgi?id=20508">20508</a>
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<th>Summary</th>
<td>basic_string does not respect NullablePointer requirements of the allocator's pointer
</td>
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<th>Product</th>
<td>libc++
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>tkoeppe@google.com
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu, mclow.lists@gmail.com
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<th>Classification</th>
<td>Unclassified
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=12843" name="attach_12843" title="Compilation failure of basic_string with fancy pointer allocator">attachment 12843</a> <a href="attachment.cgi?id=12843&action=edit" title="Compilation failure of basic_string with fancy pointer allocator">[details]</a></span>
Compilation failure of basic_string with fancy pointer allocator
I'm attaching a complete example, but the problem is easily described:
The pointer type, std::allocator_traits<A>::pointer, is not required to be
trivially constructible. In fact, it is *impossible* for this type to be
trivially constructible if it is a class type, since it must value-initialize
to the null value.
However, the current implementation of basic_string assumes that the pointer
type is trivially constructible (since it puts the type into a union without
any user-provided constructors). This makes it impossible to use basic_string
with fancy pointers.
I haven't thought too much about a solution, but I think that adding suitable
constructors to the SSO union __rep and to the type __long would make this work
and wouldn't be too invasive a change.</pre>
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