Skip to content

release/21.x: [libc++] Fix std::variant evaluating template arguments too eagerly (#151028) #153064

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Aug 18, 2025
Merged

release/21.x: [libc++] Fix std::variant evaluating template arguments too eagerly (#151028) #153064

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 5 additions & 5 deletions libcxx/include/__type_traits/invoke.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -67,20 +67,20 @@ _LIBCPP_BEGIN_NAMESPACE_STD

#if __has_builtin(__builtin_invoke)

template <class... _Args>
using __invoke_result_t _LIBCPP_NODEBUG = decltype(__builtin_invoke(std::declval<_Args>()...));

template <class, class... _Args>
struct __invoke_result_impl {};

template <class... _Args>
struct __invoke_result_impl<__void_t<__invoke_result_t<_Args...> >, _Args...> {
using type _LIBCPP_NODEBUG = __invoke_result_t<_Args...>;
struct __invoke_result_impl<__void_t<decltype(__builtin_invoke(std::declval<_Args>()...))>, _Args...> {
using type _LIBCPP_NODEBUG = decltype(__builtin_invoke(std::declval<_Args>()...));
};

template <class... _Args>
using __invoke_result _LIBCPP_NODEBUG = __invoke_result_impl<void, _Args...>;

template <class... _Args>
using __invoke_result_t _LIBCPP_NODEBUG = typename __invoke_result<_Args...>::type;

template <class... _Args>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __invoke_result_t<_Args...> __invoke(_Args&&... __args)
_NOEXCEPT_(noexcept(__builtin_invoke(std::forward<_Args>(__args)...))) {
Expand Down
16 changes: 16 additions & 0 deletions libcxx/test/std/utilities/variant/variant.variant/variant.ctor/T.pass.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -173,12 +173,28 @@ void test_vector_bool() {
assert(std::get<0>(v) == true);
}

struct ConvertibleFromAny {
template <class V>
ConvertibleFromAny(V) {}
};

int main(int, char**) {
test_T_ctor_basic();
test_T_ctor_noexcept();
test_T_ctor_sfinae();
test_no_narrowing_check_for_class_types();
test_construction_with_repeated_types();
test_vector_bool();

{ // Check that the constraints are evaluated lazily (see https://github.com/llvm/llvm-project/issues/151328)
struct Matcher {
Matcher() {}
Matcher(std::variant<ConvertibleFromAny>) {}
};

Matcher vec;
[[maybe_unused]] Matcher m = std::move(vec);
}

return 0;
}
Loading