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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Zero initialization in delegating constructor clobbers derived-class members"
href="https://llvm.org/bugs/show_bug.cgi?id=25589">25589</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Zero initialization in delegating constructor clobbers derived-class members
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</td>
</tr>
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<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++11
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>hstong@ca.ibm.com
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>In the following, the xp member of the C object should be the null
pointer-to-member value of the appropriate type because of the
zero-initialization that takes place prior to the call to the default
constructor for C.
It appears that the zero-initialization done in the delegating constructor for
A is initializing the padding as-if it was called for a most-derived object.
Online compiler: <a href="http://melpon.org/wandbox/permlink/PF2ZvaLcCTHlAKKH">http://melpon.org/wandbox/permlink/PF2ZvaLcCTHlAKKH</a>
### REPRODUCTION SCRIPT:
clang++ -x c++ -std=c++11 -<<'EOF' && ./a.out
#include <cassert>
#include <cstring>
#include <new>
struct A {
~A() { }
A() = default;
A(int) : A() { }
alignas(16) char x;
};
struct B : A {
B() : A(0) { }
};
struct C : B {
char A::*xp;
};
A a;
int main(void) {
alignas(A) unsigned char blob[sizeof(A)] = { 1, 1 };
A *ap = new (static_cast<void *>(&blob)) A(0);
assert(std::memcmp(&a, ap, sizeof a) == 0);
assert(!C().xp);
}
EOF
### ACTUAL OUTPUT:
a.out: <stdin>:26: int main(): Assertion `!C().xp' failed.
### EXPECTED OUTPUT:
(no assertion failure)
### COMPILER VERSION INFO (clang++ -v):
clang version 3.8.0 (trunk 253668)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/llvm-head/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.3
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64</pre>
</div>
</p>
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