https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105595
Bug ID: 105595
Summary: Coroutines can trigger -Wsubobject-linkage
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: blubban at gmail dot com
Target Milestone: ---
To reproduce:
- Create a minimal coroutine promise
- Create a coroutine where any local's type has no linkage (for example a
lambda)
- #include the above from another, differently named, file
Result:
/app/not_example.cpp:25:1: warning: 'foo()::_Z3foov.Frame' has a field
'foo()::_Z3foov.Frame::anon_ns_1_2' whose type uses the anonymous namespace
[-Wsubobject-linkage]
/app/not_example.cpp:25:1: warning: 'foo()::_Z3foov.Frame' has a field
'foo()::_Z3foov.Frame::inner_class_1_2' whose type has no linkage
[-Wsubobject-linkage]
/app/not_example.cpp:25:1: warning: 'foo()::_Z3foov.Frame' has a field
'foo()::_Z3foov.Frame::a_lambda_1_2' whose type has no linkage
[-Wsubobject-linkage]
Expected:
No warning, because the coroutine frame's type shouldn't have linkage either.
Sticking anonymous types inside each other is harmless.
Full testcase:
# 2 "/app/not_example.cpp" 1
#include <coroutine>
class async {
public:
class promise_type {
public:
async get_return_object() { return {}; }
std::suspend_never initial_suspend() { return {}; }
std::suspend_never final_suspend() noexcept { return {}; }
void unhandled_exception() {}
};
};
namespace {
class anon_ns_t {};
}
async foo()
{
anon_ns_t anon_ns;
class inner_class_t {} inner_class;
auto a_lambda = [](){};
co_await std::suspend_never{};
}
Compile with -std=c++20.
Compiler Explorer: https://godbolt.org/z/efz6dfoWq
