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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Local object should have unique address"
href="http://llvm.org/bugs/show_bug.cgi?id=18557">18557</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Local object should have unique address
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<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>sam@rfc1149.net
</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=11905" name="attach_11905" title="Function exhibiting the problem">attachment 11905</a> <a href="attachment.cgi?id=11905&action=edit" title="Function exhibiting the problem">[details]</a></span>
Function exhibiting the problem
[version set as "unspecified" because "3.4" does not appear in the version
selector but this happens in 3.4]
The following function
int f(int recurse, const int old[]) {
const int a[] = {1, 2, 3, 4};
if (recurse)
return f(0, a);
return a == old;
}
should always return 0 (and does so in GCC):
* If `recurse' is 0, then the newly created object `a' cannot have the same
address as `old'. LLVM makes the comparison and returns the right result, which
is not faulty but may be unnecessary.
* If `recurse' is non-0, then `a' in the first invocation and `a' in the
recursive one cannot be equal, as each automatic variable must have its own
unique address as long as it is alive. Here, LLVM returns 1 without checking
instead of 0. The problem is likely that `a' is stored in `.rodata' (then
discarded as unused) while it should not be shared between `f' can be invoked
recursively and the address of `a' escapes its defining function through the
function call.
Note that this bug was found while signaling a bug on GCC which misses an
optimization when there is no such recursive call:
<a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59863">http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59863</a></pre>
</div>
</p>
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