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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - calling string.resize(0xfffffffffffffffd) causes a segfault"
href="https://llvm.org/bugs/show_bug.cgi?id=25358">25358</a>
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<th>Summary</th>
<td>calling string.resize(0xfffffffffffffffd) causes a segfault
</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>llvm@insonuit.org
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>One of our developers found that calling string.resize(0xfffffffffffffffd)
causes a segfault.
It looks like grow_by() is rounding up that size by adding 16 bytes & then
rounding down to a multiple of 16, via __recommend(); at least on this system,
which is FreeBSD x86-64 system. That results in a zero-length allocation
request, which succeeds.
At this point, we're in trouble. append() then calls memset, via assign(), to
zero out the 2^64 bytes or so which were added; and we crash.
Perhaps grow_by() should take alignment into account when checking whether to
throw a length error, or perhaps it needs to avoid aligning if the resulting
size will wrap around 0.</pre>
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</p>
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