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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - MemorySanitizer: use-of-uninitialized-value in std::string s = "x"; std::replace(s.begin(), s.end(), 'a', 'b'); on -O0"
href="https://bugs.llvm.org/show_bug.cgi?id=50112">50112</a>
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</tr>
<tr>
<th>Summary</th>
<td>MemorySanitizer: use-of-uninitialized-value in std::string s = "x"; std::replace(s.begin(), s.end(), 'a', 'b'); on -O0
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>10.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</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>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>nok.raven@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>#include <string>
int main()
{
std::string s = "x";
std::replace(s.begin(), s.end(), 'a', 'b');
}
clang++-11 -fsanitize=memory -stdlib=libc++ -g z.cpp -o z && ./z
==62635==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x49a95b in std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::__get_pointer()
/usr/lib/llvm-11/bin/../include/c++/v1/string:1514:17
#1 0x49a461 in std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::begin()
/usr/lib/llvm-11/bin/../include/c++/v1/string:909:26
#2 0x499d79 in main /home/user/z.cpp:6:20
#3 0x7fcd8bd35cb1 in __libc_start_main csu/../csu/libc-start.c:314:16
#4 0x41d26d in _start (/home/user/z+0x41d26d)
SUMMARY: MemorySanitizer: use-of-uninitialized-value
/usr/lib/llvm-11/bin/../include/c++/v1/string:1514:17 in
std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::__get_pointer()
Exiting
Clang/libc++ 10+ are affected
<a href="https://godbolt.org/z/6E9aeWjjP">https://godbolt.org/z/6E9aeWjjP</a></pre>
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