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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 --- - Sigsegv in exception::what() after r"
href="http://llvm.org/bugs/show_bug.cgi?id=18403">18403</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Sigsegv in exception::what() after r
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>hhinnant@apple.com
</td>
</tr>
<tr>
<th>Reporter</th>
<td>jonathan.sauer@gmx.de
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following program, when compiled with clang r198596 and libc++ r198635
(which was also compiled with clang r198596), crashes with a SIGSEGV when run:
#include <cstdio>
#include <stdexcept>
int main()
{
try
{
throw std::runtime_error("Error");
}
catch (const std::exception& e)
{
std::printf("%s\n", e.what());
}
}
This results in:
% ~/LLVM/build/Release+Asserts/bin/clang++ -std=c++11 -stdlib=libc++ clang.cpp
% gdb ./a.out
[...]
(gdb) r
[...]
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000000000000
0x00000001000425e6 in std::runtime_error::what ()
(gdb) bt
#0 0x00000001000425e6 in std::runtime_error::what ()
#1 0x0000000100000da3 in main ()
After reverting to r198504 (before the last change to stdexcept.cpp), the code
ran fine.
I suspect the cause of the crash lies in the following change in
stdexcept.cpp[*]:
runtime_error::runtime_error(const runtime_error& le) _NOEXCEPT
{
- __libcpp_nmstr& s = (__libcpp_nmstr&)__imp_;
- ::new(&s) __libcpp_nmstr((const __libcpp_nmstr&)le.__imp_);
+ __libcpp_nmstr *s = static_cast<__libcpp_nmstr *>(__imp_);
+ const __libcpp_nmstr *s2 = static_cast<const __libcpp_nmstr *>(le.__imp_);
+ ::new(s) __libcpp_nmstr(*s2);
}
Before the new "__libcpp_nmstr" was created inside "__imp_" (as "s" was a
reference to it, and taking the address of a reference means taking the address
of the referenced variable, i.e. "__imp_"). Now the new string is created
inside "s" and never gets stored in "__imp_".
Proposed fix: Remove "s" and just say:
::new(__imp_) __libcpp_nmstr(*s2);
(same in the other constructors as well)
[*]
<<a href="http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/stdexcept.cpp?r1=198505&r2=198504&pathrev=198505">http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/stdexcept.cpp?r1=198505&r2=198504&pathrev=198505</a>></pre>
</div>
</p>
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