<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - clang++ miscompiles against MSVC standard library with -O2"
href="https://bugs.llvm.org/show_bug.cgi?id=43710">43710</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>clang++ miscompiles against MSVC standard library with -O2
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>9.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>other
</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>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>karen@codesynthesis.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=22688" name="attach_22688" title="Test program">attachment 22688</a> <a href="attachment.cgi?id=22688&action=edit" title="Test program">[details]</a></span>
Test program
Hello,
My system is Windows 10 with clang 9.0.0 (installed with
<a href="https://releases.llvm.org/9.0.0/LLVM-9.0.0-win64.exe">https://releases.llvm.org/9.0.0/LLVM-9.0.0-win64.exe</a>) and Microsoft Visual
Studio Community 2019, Version 16.3.1.
Under some circumstances a non-empty string passed into a function is seen by
the function code as an empty string.
The attached program reproduces the issue. It is expected to print 'abc' but
prints '' if compiled with -O2 or -O3:
<span class="quote">> clang++ -std=c++2a test.cxx
> a.exe</span >
'abc'
<span class="quote">>clang++ -std=c++2a -O2 test.cxx
>a.exe</span >
''
Note that the issue also reproduces if compile with clang-cl:
<span class="quote">> clang-cl /std:c++17 /EHsc test.cxx
> test.exe</span >
'abc'
<span class="quote">> clang-cl /std:c++17 /EHsc /O2 test.cxx
> test.exe</span >
''
Also note that the attached program is not exactly trivial but I was unable to
reduce it further.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>