https://bugs.llvm.org/show_bug.cgi?id=52322
Bug ID: 52322
Summary: C++20 warning: template lambda "does not declare any
constructor to initialize its non-modifiable members"
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Frontend
Assignee: unassignedclangb...@nondot.org
Reporter: jake.arkinst...@gmail.com
CC: llvm-bugs@lists.llvm.org, neeil...@live.com,
richard-l...@metafoo.co.uk
In this toy code, clang 13 warns that a lambda function isn't initializing
captured members.
https://godbolt.org/z/hhszT4fqj
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).
> <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>() {
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