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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Unused code triggers linker failure"
href="https://bugs.llvm.org/show_bug.cgi?id=38029">38029</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Unused code triggers linker failure
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>6.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Other
</td>
</tr>
<tr>
<th>OS</th>
<td>FreeBSD
</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>C++
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>adridg@FreeBSD.org
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>This program fails to link (clang6 on FreeBSD):
```
#include <string>
static std::string f() { return std::string(); }
int main() { (void) f; }
```
The error message is
```
/tmp/t-a76eba.o: In function `f()':
t.cpp:(.text+0x20): undefined reference to `std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> >::basic_string()'
/usr/bin/ld: a.out: hidden symbol
`_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEC2Ev' isn't
defined
/usr/bin/ld: final link failed: Nonrepresentable section on output
```
It also fails with clang5 on FreeBSD, on FreeBSDs 11- and 12-, and reportedly
on Linux with clang6 and -stdlib=libc++.
It doesn't fail with -O1 or above. It doesn't fail if you remove the `(void)f;`
statement, although then you will get an unused function warning.
Also reported downstream as
<a href="https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=229479">https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=229479</a></pre>
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