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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - StackAddressEscape doesn't properly lifetime extend temporaries bound to static variables"
href="https://bugs.llvm.org/show_bug.cgi?id=37547">37547</a>
</td>
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<tr>
<th>Summary</th>
<td>StackAddressEscape doesn't properly lifetime extend temporaries bound to static variables
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</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>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Static Analyzer
</td>
</tr>
<tr>
<th>Assignee</th>
<td>dcoughlin@apple.com
</td>
</tr>
<tr>
<th>Reporter</th>
<td>george.burgess.iv@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Test-case:
$ cat /tmp/f.cpp
struct Foo {
Foo();
~Foo();
int i;
};
const void *foo() {
static const Foo &f = {};
return &f;
}
$ clang-tidy -checks=clang-analyzer-core.StackAddressEscape /tmp/f.cpp --
2 warnings generated.
/tmp/f.cpp:9:3: warning: Address of stack memory associated with temporary
object of type 'Foo' returned to caller
[clang-analyzer-core.StackAddressEscape]
return &f;
^
/tmp/f.cpp:9:3: note: Address of stack memory associated with temporary object
of type 'Foo' returned to caller
/tmp/f.cpp:10:1: warning: Address of stack memory associated with temporary
object of type 'Foo' is still referred to by the static variable 'f' upon
returning to the caller. This will be a dangling reference
[clang-analyzer-core.StackAddressEscape]
}
^
/tmp/f.cpp:10:1: note: Address of stack memory associated with temporary object
of type 'Foo' is still referred to by the static variable 'f' upon returning to
the caller. This will be a dangling reference
----------------
Reading the C++ standard, however, it appears that temporary lifetime extension
extends the lifetime of temporaries to live as long as the reference they're
being bound to. So, since `f` is static, the temporary being bound to it gets
to live until the program dies: <a href="https://godbolt.org/g/snsWA7">https://godbolt.org/g/snsWA7</a> (please note the
atexit dtor call and extra global `_ZGRZ3foovE1f_`)
For added fun, this appears to apply to struct fields, too:
<a href="https://godbolt.org/g/NdV7jW">https://godbolt.org/g/NdV7jW</a>
(FWIW, the struct fields example is a reduced version of how I found this. When
I first saw it, I thought the code was broken, too. :) )</pre>
</div>
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