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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - C++20 warning: template lambda "does not declare any constructor to initialize its non-modifiable members""
href="https://bugs.llvm.org/show_bug.cgi?id=52322">52322</a>
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<th>Summary</th>
<td>C++20 warning: template lambda "does not declare any constructor to initialize its non-modifiable members"
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<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>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Frontend
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>jake.arkinstall@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<pre>In this toy code, clang 13 warns that a lambda function isn't initializing
captured members.
<a href="https://godbolt.org/z/hhszT4fqj">https://godbolt.org/z/hhszT4fqj</a>
I don't know whether (1) this is a false positive warning, (2) the warning is
legitimate and the generated code is incorrect, or (3) the code is truly
invalid and the warning is a side-effect of that.
I'm leaning towards #1. I'd rule #2 out because it still produces the correct
output, and I'd (tentatively) rule #3 out because GCC and MSVC don't see any
problems with the code (Clang 12 segfaults on it, which appears to be a parsing
issue).
<span class="quote">> <source>:9:48: warning: class '' does not declare any constructor to initialize its non-modifiable members
> TypeList<tail...>::max(comparison, [&comparison, &callback]<typename S>() {
> ^
> <source>:9:48: note: in instantiation of member class '' requested here
> <source>:17:31: note: in instantiation of function template specialization 'TypeList<int, char>::max((lambda at <source>:34:9) &, (lambda at <source>:9:48) &&)::(anonymous class)::operator()<char>' requested here
> callback.template operator()<head>();
> ^
> <source>:9:32: note: in instantiation of function template specialization 'TypeList<char>::max<(lambda at <source>:34:9) &, (lambda at <source>:9:48)>' requested here
> TypeList<tail...>::max(comparison, [&comparison, &callback]<typename S>() {
> ^
> <source>:9:32: note: in instantiation of function template specialization 'TypeList<int, char>::max<(lambda at <source>:34:9) &, (lambda at <source>:9:48)>' requested here
> <source>:33:11: note: in instantiation of function template specialization 'TypeList<long, int, char>::max<(lambda at <source>:34:9), (lambda at <source>:35:9)>' requested here
> list::max(
> ^
> <source>:9:50: note: reference member '' will never be initialized
> TypeList<tail...>::max(comparison, [&comparison, &callback]<typename S>() {
> ^
> <source>:9:63: note: reference member '' will never be initialized
> TypeList<tail...>::max(comparison, [&comparison, &callback]<typename S>() {</span ></pre>
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