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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Invalid optimization involving malloc and pointer aliasing"
href="https://bugs.llvm.org/show_bug.cgi?id=44931">44931</a>
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<th>Summary</th>
<td>Invalid optimization involving malloc and pointer aliasing
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>9.0
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>pskocik@gmail.com
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
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<pre>Sort of contrived, but this code:
int use_malloc(int * X, void ** R, size_t Sz)
{
*X = 42;
*R = malloc(Sz);
return *X;
}
is getting unconditionally optimized to return 42 on clang (not on gcc).
This is an invalid optimization considering that the function can be called
with use_malloc(&errno, ...) and malloc will set errno on failure.
Failing test case:
<a href="https://gcc.godbolt.org/z/sEEBpJ">https://gcc.godbolt.org/z/sEEBpJ</a></pre>
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