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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Bounds sanitizer instruments [0] array inside a union"
href="https://bugs.llvm.org/show_bug.cgi?id=45030">45030</a>
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<th>Summary</th>
<td>Bounds sanitizer instruments [0] array inside a union
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>-New Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>lenaptr@google.com
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
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<pre>It looks like bounds sanitizer treats unions as structs, and all flex arrays
except for the last one are being checked (while none of them should):
```
#include <stdlib.h>
typedef union {
char foo[0];
void *bar[0];
void *buz[0];
} flexi;
void repro(int i) {
flexi *a = (flexi*) malloc(50);
a->foo[i] = 0; // this will be instrumented
a->bar[i] = 0; // this will be instrumented
a->buz[i] = 0; // this won't be instrumented
free(a);
}
```
Compile with `-fsanitize=bounds`
->bar and ->buz are semantically the same, but only one of them gets flex array
exception. ->foo also shouldn't be instrumented.</pre>
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