Check range_begin is dereferenceable (#3964)

Fixes issue #3839
An Eigen 3.4 2x2 matrix has a begin member function that returns void
Be more strict checking that the result of calling *begin() is valid
See input_or_output_iterator concept notes about void
This commit is contained in:
Justin Riddell 2024-05-21 00:11:07 +01:00 committed by GitHub
parent 706eabd5e5
commit b81761068b
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
2 changed files with 12 additions and 6 deletions

View File

@ -68,7 +68,7 @@ template <typename T, typename Enable = void>
struct has_member_fn_begin_end_t : std::false_type {};
template <typename T>
struct has_member_fn_begin_end_t<T, void_t<decltype(std::declval<T>().begin()),
struct has_member_fn_begin_end_t<T, void_t<decltype(*std::declval<T>().begin()),
decltype(std::declval<T>().end())>>
: std::true_type {};
@ -99,15 +99,15 @@ struct has_mutable_begin_end : std::false_type {};
template <typename T>
struct has_const_begin_end<
T,
void_t<
decltype(detail::range_begin(std::declval<const remove_cvref_t<T>&>())),
decltype(detail::range_end(std::declval<const remove_cvref_t<T>&>()))>>
T, void_t<decltype(*detail::range_begin(
std::declval<const remove_cvref_t<T>&>())),
decltype(detail::range_end(
std::declval<const remove_cvref_t<T>&>()))>>
: std::true_type {};
template <typename T>
struct has_mutable_begin_end<
T, void_t<decltype(detail::range_begin(std::declval<T&>())),
T, void_t<decltype(*detail::range_begin(std::declval<T&>())),
decltype(detail::range_end(std::declval<T&>())),
// the extra int here is because older versions of MSVC don't
// SFINAE properly unless there are distinct types

View File

@ -742,3 +742,9 @@ TEST(ranges_test, movable_only_istream_iter_join) {
EXPECT_EQ("1, 2, 3, 4, 5",
fmt::format("{}", fmt::join(std::move(first), last, ", ")));
}
struct not_range {
void begin() const {}
void end() const {}
};
static_assert(!fmt::is_formattable<not_range>{}, "");