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<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - MemorySanitizer false positive with -O2 or higher"
href="http://llvm.org/bugs/show_bug.cgi?id=22077">22077</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>MemorySanitizer false positive with -O2 or higher
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.5
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</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>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>oliverst@online.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>Created <span class=""><a href="attachment.cgi?id=13616" name="attach_13616" title="preprocessed C source code">attachment 13616</a> <a href="attachment.cgi?id=13616&action=edit" title="preprocessed C source code">[details]</a></span>
preprocessed C source code
This code
#include <string>
void func(const char* s)
{
if(s== NULL)
{
}
}
int main()
{
func((std::string("const ") + "manager").c_str());
return 0;
}
generates the following warning when compiled with "-fsanitize=memory
-fsanitize-memory-track-origins -O2". It also happens with -O3, but not with
-O1 or without optimizations.
==13491== WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x7f74e825e04b in main (/home/notroot/trunk/a.out+0x8f04b)
#1 0x7f74e6dbbec4 in __libc_start_main
/build/buildd/eglibc-2.19/csu/libc-start.c:287
#2 0x7f74e825da5c in _start (/home/notroot/trunk/a.out+0x8ea5c)
Uninitialized value was created by an allocation of '' in the stack frame of
function 'main'
#0 0x7f74e825db60 in main (/home/notroot/trunk/a.out+0x8eb60)
SUMMARY: MemorySanitizer: use-of-uninitialized-value ??:0 main
I am using the official clang 3.5 binaries from llvm.org on ubuntu 14.04.
clang version 3.5.0 (tags/RELEASE_350/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.1
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Candidate multilib: .;@m64
Selected multilib: .;@m64</pre>
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