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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 - Function in non-type template param causes undefined reference with debug build"
href="https://bugs.llvm.org/show_bug.cgi?id=45804">45804</a>
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<th>Summary</th>
<td>Function in non-type template param causes undefined reference with debug build
</td>
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<th>Product</th>
<td>clang
</td>
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<tr>
<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>lightborn@gmail.com
</td>
</tr>
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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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<pre>```cpp
void func1(int x);
template<void(&f)(int)>
void func2() { }
int main() {
func2<func1>();
}
```
clang++-9 ref.cxx -g
/tmp/ref-970157.o:(.debug_info+0x67): undefined reference to `func1(int)'
clang: error: linker command failed with exit code 1 (use -v to see invocation
The LLVM function symbol in DITemplateValueParameter apparently ODR uses that
function:
!DITemplateValueParameter(name: "f", type: !18, value: void (i32)* @_Z5func1i)
For non-type template params that bind to a declaration, it seems you can just
pass an appropriately typed nullptr as the Val argument of
DIBuilder::createTemplateValueParameter:
!DITemplateValueParameter(name: "f", type: !18, value: void (i32)* null)
Of course when you pass null you lose introspection of the parameter in the
debugger.
gcc manages to get the best of both worlds somehow:
If func1 is undefined the program still links, but there's no introspection of
f in the debugger.
If func2 is externally defined.. or its defined as inline and ODR used inside
the TU, it both links and gives you introspection in the debugger.</pre>
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