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<base href="https://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 --- - Atomic compare_exchange_weak/strong"
href="https://llvm.org/bugs/show_bug.cgi?id=25500">25500</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Atomic compare_exchange_weak/strong
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>3.7
</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>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>venkat.murty@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=15269" name="attach_15269" title="A test c++ code that shows the bug. It spawns 8 threads.">attachment 15269</a> <a href="attachment.cgi?id=15269&action=edit" title="A test c++ code that shows the bug. It spawns 8 threads.">[details]</a></span>
A test c++ code that shows the bug. It spawns 8 threads.
The following snippet does not work as expected.
struct Node { Node* next; };
std::atomic<Node*> head (nullptr);
// Is like free
void push (void* p)
{
Node* n = (Node*) p;
n->next = head.load ();
while (!head.compare_exchange_strong (n->next, n));
}
// is like malloc
void* pop ()
{
Node* n = head.load ();
while (n &&
!head.compare_exchange_strong (n, n->next));
return n ? n : malloc (SIZE);
}
The attached file with the driver crashes every 1 in 5 times.
clang++ -g -std=c++11 test.cpp</pre>
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