Skip to content

🐛 Fix make_array for zero-length cases #338

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
elbeno merged 1 commit into from
Mar 15, 2026
Merged

🐛 Fix make_array for zero-length cases #338

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
6 changes: 4 additions & 2 deletions include/stdx/array.hpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@ template <typename D = void, typename... Ts>
constexpr auto make_array(Ts &&...ts) {
if constexpr (not std::is_void_v<D>) {
return std::array<D, sizeof...(Ts)>{std::forward<Ts>(ts)...};
} else if constexpr (sizeof...(Ts) == 0) {
return std::array<int, 0>{};
} else {
using A = std::common_type_t<Ts...>;
return std::array<A, sizeof...(Ts)>{std::forward<Ts>(ts)...};
Expand All @@ -19,7 +21,7 @@ constexpr auto make_array(Ts &&...ts) {

template <template <auto> typename D, typename T, T... Is>
constexpr auto make_array(std::integer_sequence<T, Is...>) {
using A = std::common_type_t<decltype(D<Is>::value)...>;
using A = std::remove_const_t<decltype(D<T{}>::value)>;
return std::array<A, sizeof...(Is)>{D<Is>::value...};
}

Expand All @@ -29,7 +31,7 @@ template <template <auto> typename D, auto N> constexpr auto make_array() {

template <typename T, T... Is, typename F>
constexpr auto make_array(std::integer_sequence<T, Is...>, F &&f) {
using A = std::common_type_t<decltype(f.template operator()<Is>())...>;
using A = std::remove_const_t<decltype(f.template operator()<T{}>())>;
return std::array<A, sizeof...(Is)>{f.template operator()<Is>()...};
}

Expand Down
34 changes: 34 additions & 0 deletions test/array.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,16 @@ TEST_CASE("make_array (variadic arguments)", "[array]") {
CHECK(arr == std::array{1, 2, 3, 4, 5});
}

TEST_CASE("make_array (zero case)", "[array]") {
auto arr = stdx::make_array<float>();
STATIC_CHECK(std::is_same_v<decltype(arr), std::array<float, 0>>);
}

TEST_CASE("make_array (zero case default)", "[array]") {
auto arr = stdx::make_array();
STATIC_CHECK(std::is_same_v<decltype(arr), std::array<int, 0>>);
}

namespace {
template <auto I> using V = std::integral_constant<decltype(I), I + 1>;
}
Expand All @@ -20,12 +30,24 @@ TEST_CASE("make_array by sequence (template with ::value)", "[array]") {
CHECK(arr == std::array{1, 2, 3, 4, 5});
}

TEST_CASE("make_array by sequence - zero case (template with ::value)",
"[array]") {
auto arr = stdx::make_array<V>(std::make_integer_sequence<int, 0>{});
STATIC_CHECK(std::is_same_v<decltype(arr), std::array<int, 0>>);
}

TEST_CASE("make_array by extent (template with ::value)", "[array]") {
auto arr = stdx::make_array<V, 5>();
STATIC_CHECK(std::is_same_v<decltype(arr), std::array<int, 5>>);
CHECK(arr == std::array{1, 2, 3, 4, 5});
}

TEST_CASE("make_array by extent - zero case (template with ::value)",
"[array]") {
auto arr = stdx::make_array<V, 0>();
STATIC_CHECK(std::is_same_v<decltype(arr), std::array<int, 0>>);
}

namespace {
struct {
template <auto I> auto operator()() { return I + 1; }
Expand All @@ -38,8 +60,20 @@ TEST_CASE("make_array by sequence (factory function template)", "[array]") {
CHECK(arr == std::array{1, 2, 3, 4, 5});
}

TEST_CASE("make_array by sequence - zero case (factory function template)",
"[array]") {
auto arr = stdx::make_array(std::make_integer_sequence<int, 0>{}, f);
STATIC_CHECK(std::is_same_v<decltype(arr), std::array<int, 0>>);
}

TEST_CASE("make_array by extent (factory function template)", "[array]") {
auto arr = stdx::make_array<5>(f);
STATIC_CHECK(std::is_same_v<decltype(arr), std::array<int, 5>>);
CHECK(arr == std::array{1, 2, 3, 4, 5});
}

TEST_CASE("make_array by extent - zero case (factory function template)",
"[array]") {
auto arr = stdx::make_array<0>(f);
STATIC_CHECK(std::is_same_v<decltype(arr), std::array<int, 0>>);
}