<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 --- - warn on c-style cast that changes meaning after definition"
href="http://llvm.org/bugs/show_bug.cgi?id=22181">22181</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>warn on c-style cast that changes meaning after definition
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</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>C++
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>nlewycky@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Testcase from <a href="http://whatofhow.wordpress.com/2014/12/17/evil-casts/">http://whatofhow.wordpress.com/2014/12/17/evil-casts/</a> :
struct S1 { int s1 = 2; };
struct S2;
S2 *f(S1 *s) { return (S2*) s; }
struct T { int t = 1; };
struct S2 : T, S1 {};
int main() { S2 s2; return f(&s2)->t; }
This code builds in -std=c++11 with no interesting warnings. The problem is in
the definition of 'f' which casts to a pointer to incomplete class type. The
std says "It is unspecified whether a static_cast or reinterpret_cast
interpretation is used, even if there is an inheritance relationship between
the two classes."
If we have a C-style cast to a point to an incomplete class type, then when we
see the definition of the class type we should check whether the static_cast
and reinterpret_cast interpretations would have had different semantics.</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>