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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - UBSan SEGFAULTs rendering memory at 0x00000001"
href="http://llvm.org/bugs/show_bug.cgi?id=18058">18058</a>
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<th>Summary</th>
<td>UBSan SEGFAULTs rendering memory at 0x00000001
</td>
</tr>
<tr>
<th>Product</th>
<td>compiler-rt
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>compiler-rt
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>tim.besard@elis.ugent.be
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>I'm trying to run some code through UBSan, but it crashes when trying to print
memory at address 0x00000001. The code in question comes from
boost::serialization 1.54:
boost/serialization/void_cast.hpp:187:13
// note:I wanted to display from 0 here, but at least one compiler
// treated 0 by not shifting it at all.
reinterpret_cast<std::ptrdiff_t>(
static_cast<Derived *>(
reinterpret_cast<Base *>(1)
)
) - 1
UBSan crashes because it detects a misaligned downcasts, after which it tries
to read the memory at 0xx00000001:
/boost/serialization/void_cast.hpp:187:13: runtime error: downcast of
misaligned address 0x00000001 for type 'BundleRFRead',
which requires 4 byte alignment
0x00000001: note: pointer points here
Program received signal SIGSEGV, Segmentation fault.
0x089c36dd in getMemoryLocation () at
llvm/projects/compiler-rt/lib/ubsan/ubsan_diag.cc:191
191 Printf("%s%02x", (P % 8 == 0) ? " " : " ", C);
This is on ToT, with the backtrace as follows:
#0 0x089c36dd in getMemoryLocation ()
at llvm/projects/compiler-rt/lib/ubsan/ubsan_diag.cc:191
#1 ~Diag ()
at llvm/projects/compiler-rt/lib/ubsan/ubsan_diag.cc:271
#2 0x089c412f in handleTypeMismatchImpl ()
at llvm/projects/compiler-rt/lib/ubsan/ubsan_handlers.cc:52
#3 0x089c3b8f in __ubsan_handle_type_mismatch ()
at llvm/projects/compiler-rt/lib/ubsan/ubsan_handlers.cc:56</pre>
</div>
</p>
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