<html>
<head>
<base href="http://llvm.org/bugs/" />
</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 --- - Undetected use of uninitialised variable (detected at -O2 -Wall by gcc)"
href="http://llvm.org/bugs/show_bug.cgi?id=17940">17940</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Undetected use of uninitialised variable (detected at -O2 -Wall by gcc)
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.3
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Macintosh
</td>
</tr>
<tr>
<th>OS</th>
<td>MacOS X
</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>christophe@taodyne.com
</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=11543" name="attach_11543" title="Source code example">attachment 11543</a> <a href="attachment.cgi?id=11543&action=edit" title="Source code example">[details]</a></span>
Source code example
At -O2 or above, GCC 4.2 detects that the 'result' variable can be used
uninitialised in the attached code. clang 3.3svn (as shipped with OSX) does
not.
Compile with "true" g++ -O2 -Wall:
g++ -Wall -O2 -c /tmp/glop.cpp
/tmp/glop.cpp: In function 'char* undetected()':
/tmp/glop.cpp:6: warning: 'result' may be used uninitialized in this function
With llvm-g++, there is no message.
Reduced test case:
extern bool dont_stop();
extern char *data(unsigned);
char *undetected()
{
char *result;
for (unsigned count = 0; count < 2 && dont_stop(); count++)
result = data(count);
return result;
}</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>