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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - ASAN use-after-scope for thread-local variables"
href="https://bugs.llvm.org/show_bug.cgi?id=47616">47616</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>ASAN use-after-scope for thread-local variables
</td>
</tr>
<tr>
<th>Product</th>
<td>compiler-rt
</td>
</tr>
<tr>
<th>Version</th>
<td>11.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>asan
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>mvanotti@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>It seems like asan is not keeping track of thread-local variables.
```cpp
#include <iostream>
#include <thread>
thread_local int x;
extern "C" int __asan_address_is_poisoned(void const volatile *addr);
extern "C" void __asan_describe_address(void *addr);
extern "C" void __asan_poison_memory_region(void const volatile *addr, size_t
size);
int main() {
std::cout << __asan_address_is_poisoned(&x) << " " <<
__asan_address_is_poisoned(&x + 1) << " " << __asan_address_is_poisoned(&x -
1) << std::endl;
int* p = nullptr;
x = 1;
std::thread([&p]() {
x = 2;
p = &x;
std::cout << __asan_address_is_poisoned(p) << " " <<
__asan_address_is_poisoned(p + 1) << " " << __asan_address_is_poisoned(p -
1) << std::endl;
__asan_poison_memory_region(p, sizeof(*p));
std::cout << __asan_address_is_poisoned(p) << " " <<
__asan_address_is_poisoned(p + 1) << " " << __asan_address_is_poisoned(p -
1) << std::endl;
__asan_describe_address(p);
}).join();
std::cout << &x << " " << &p << std::endl;
std::cout << __asan_address_is_poisoned(&x) << " " <<
__asan_address_is_poisoned(p) << std::endl;
__asan_describe_address(&x);
__asan_describe_address(p);
std::cout << x << " " << *p << std::endl;
return 0;
}
```
In this example, we are running a thread that takes the address of a
thread-local variable and it checks whether the local variable is poisoned
after the thread ends. It is not.</pre>
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