https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107556
Bug ID: 107556
Summary: Passing lambda to a coroutine function triggers
-Wsubobject-linkage
Product: gcc
Version: 10.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dennis-hezel at gmx dot de
Target Milestone: ---
Affects GCC 10+
If you think the warning is legitimate then please advise how to change the
code.
Smallest reproducer I could come up with: https://godbolt.org/z/WvPE1qx8s
It is not limited to `co_yield`, `co_await`-compatible coroutines also trigger
it.
Reproducer here incase the compiler explorer link does not work:
other.hpp
```c++
#include <coroutine>
struct Generator
{
struct promise_type
{
Generator get_return_object() { return Generator{}; }
std::suspend_always initial_suspend() { return {}; }
std::suspend_always final_suspend() noexcept { return {}; }
std::suspend_always yield_value(int) { return {}; }
void unhandled_exception() {}
};
};
template <class F>
auto invoke_and_await(F) -> Generator
{
co_yield 1;
}
auto test()
{
invoke_and_await([] {});
}
```
main.cpp
```c++
// must be included, copy-pasting the code into here won't trigger it
#include "other.hpp"
```
Compiler output:
```
In file included from /app/main.cpp:2:
other.hpp: In instantiation of 'Generator invoke_and_await(F) [with F =
test()::<lambda()>]':
other.hpp:23:27: required from here
other.hpp:19:1: warning: 'invoke_and_await<test()::<lambda()>
>::_Z16invoke_and_awaitIZ4testvEUlvE_E9GeneratorT_.frame' has a field
'invoke_and_await<test()::<lambda()>
>::_Z16invoke_and_awaitIZ4testvEUlvE_E9GeneratorT_.frame::__unnamed_parm.0'
whose type has no linkage [-Wsubobject-linkage]
19 | }
| ^
```
Compile with `-fcoroutines` before GCC version 11.
