diff --git a/libcxx/test/std/containers/views/mdspan/ConvertibleToIntegral.h b/libcxx/test/std/containers/views/mdspan/ConvertibleToIntegral.h
index 2f081c38ef65f..470f5d8e72464 100644
--- a/libcxx/test/std/containers/views/mdspan/ConvertibleToIntegral.h
+++ b/libcxx/test/std/containers/views/mdspan/ConvertibleToIntegral.h
@@ -17,7 +17,7 @@ struct IntType {
   constexpr bool operator==(const IntType& rhs) const { return val == rhs.val; }
   constexpr operator int() const noexcept { return val; }
   constexpr operator unsigned char() const { return val; }
-  constexpr operator char() const noexcept { return val; }
+  constexpr operator signed char() const noexcept { return val; }
 };
 
 // only non-const convertible
diff --git a/libcxx/test/std/containers/views/mdspan/extents/CtorTestCombinations.h b/libcxx/test/std/containers/views/mdspan/extents/CtorTestCombinations.h
index 5ad841f16939a..bf08c580f3746 100644
--- a/libcxx/test/std/containers/views/mdspan/extents/CtorTestCombinations.h
+++ b/libcxx/test/std/containers/views/mdspan/extents/CtorTestCombinations.h
@@ -89,11 +89,11 @@ constexpr bool test_index_type_combo() {
   test<int, int, Test>();
   test<int, size_t, Test>();
   test<unsigned, int, Test>();
-  test<char, size_t, Test>();
+  test<signed char, size_t, Test>();
   test<long long, unsigned, Test>();
   test<size_t, int, Test>();
   test<size_t, size_t, Test>();
   test<int, IntType, Test>();
-  test<char, IntType, Test>();
+  test<signed char, IntType, Test>();
   return true;
 }
diff --git a/libcxx/test/std/containers/views/mdspan/extents/obs_static.pass.cpp b/libcxx/test/std/containers/views/mdspan/extents/obs_static.pass.cpp
index 90b482b3bc065..0c8d3415a6726 100644
--- a/libcxx/test/std/containers/views/mdspan/extents/obs_static.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/extents/obs_static.pass.cpp
@@ -81,7 +81,7 @@ void test() {
 int main(int, char**) {
   test<int>();
   test<unsigned>();
-  test<char>();
+  test<signed char>();
   test<long long>();
   test<size_t>();
   return 0;
diff --git a/libcxx/test/std/containers/views/mdspan/extents/types.pass.cpp b/libcxx/test/std/containers/views/mdspan/extents/types.pass.cpp
index 2281945333999..dbaff46e82b6b 100644
--- a/libcxx/test/std/containers/views/mdspan/extents/types.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/extents/types.pass.cpp
@@ -78,7 +78,7 @@ void test() {
 int main(int, char**) {
   test<int>();
   test<unsigned>();
-  test<char>();
+  test<signed char>();
   test<long long>();
   test<size_t>();
   return 0;
diff --git a/libcxx/test/std/containers/views/mdspan/layout_left/extents.verify.cpp b/libcxx/test/std/containers/views/mdspan/layout_left/extents.verify.cpp
index a1e308f00ae56..b976ed7295db3 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_left/extents.verify.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_left/extents.verify.cpp
@@ -29,5 +29,5 @@ void not_extents() {
 
 void representable() {
   // expected-error-re@*:* {{static assertion failed {{.*}}layout_left::mapping product of static extents must be representable as index_type.}}
-  [[maybe_unused]] std::layout_left::mapping<std::extents<char, 20, 20>> mapping;
+  [[maybe_unused]] std::layout_left::mapping<std::extents<signed char, 20, 20>> mapping;
 }
diff --git a/libcxx/test/std/containers/views/mdspan/layout_left/index_operator.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_left/index_operator.pass.cpp
index 5ca6f65e510d3..1b6cb5ab3fb25 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_left/index_operator.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_left/index_operator.pass.cpp
@@ -80,7 +80,7 @@ constexpr bool test() {
   test_iteration<std::extents<unsigned, D>>(7);
   test_iteration<std::extents<unsigned, 7>>();
   test_iteration<std::extents<unsigned, 7, 8>>();
-  test_iteration<std::extents<char, D, D, D, D>>(1, 1, 1, 1);
+  test_iteration<std::extents<signed char, D, D, D, D>>(1, 1, 1, 1);
 
   // Check operator constraint for number of arguments
   static_assert(check_operator_constraints(std::layout_left::mapping<std::extents<int, D>>(std::extents<int, D>(1)), 0));
diff --git a/libcxx/test/std/containers/views/mdspan/layout_left/properties.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_left/properties.pass.cpp
index 85a362fc41d25..cbf1b5c290766 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_left/properties.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_left/properties.pass.cpp
@@ -53,7 +53,7 @@ constexpr void test_layout_mapping_left() {
 constexpr bool test() {
   constexpr size_t D = std::dynamic_extent;
   test_layout_mapping_left<std::extents<int>>();
-  test_layout_mapping_left<std::extents<char, 4, 5>>();
+  test_layout_mapping_left<std::extents<signed char, 4, 5>>();
   test_layout_mapping_left<std::extents<unsigned, D, 4>>();
   test_layout_mapping_left<std::extents<size_t, D, D, D, D>>();
   return true;
diff --git a/libcxx/test/std/containers/views/mdspan/layout_left/static_requirements.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_left/static_requirements.pass.cpp
index 366498803a2de..23a7c8a09005c 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_left/static_requirements.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_left/static_requirements.pass.cpp
@@ -124,7 +124,7 @@ void test_layout_mapping_left() {
 int main(int, char**) {
   constexpr size_t D = std::dynamic_extent;
   test_layout_mapping_left<std::extents<int>>();
-  test_layout_mapping_left<std::extents<char, 4, 5>>();
+  test_layout_mapping_left<std::extents<signed char, 4, 5>>();
   test_layout_mapping_left<std::extents<unsigned, D, 4>>();
   test_layout_mapping_left<std::extents<size_t, D, D, D, D>>();
   return 0;
diff --git a/libcxx/test/std/containers/views/mdspan/layout_right/extents.verify.cpp b/libcxx/test/std/containers/views/mdspan/layout_right/extents.verify.cpp
index aad91ae6d46f1..c0d1876dca441 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_right/extents.verify.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_right/extents.verify.cpp
@@ -29,5 +29,5 @@ void not_extents() {
 
 void representable() {
   // expected-error-re@*:* {{static assertion failed {{.*}}layout_right::mapping product of static extents must be representable as index_type.}}
-  [[maybe_unused]] std::layout_right::mapping<std::extents<char, 20, 20>> mapping;
+  [[maybe_unused]] std::layout_right::mapping<std::extents<signed char, 20, 20>> mapping;
 }
diff --git a/libcxx/test/std/containers/views/mdspan/layout_right/index_operator.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_right/index_operator.pass.cpp
index 19072658889ee..879e6713376d6 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_right/index_operator.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_right/index_operator.pass.cpp
@@ -80,7 +80,7 @@ constexpr bool test() {
   test_iteration<std::extents<unsigned, D>>(7);
   test_iteration<std::extents<unsigned, 7>>();
   test_iteration<std::extents<unsigned, 7, 8>>();
-  test_iteration<std::extents<char, D, D, D, D>>(1, 1, 1, 1);
+  test_iteration<std::extents<signed char, D, D, D, D>>(1, 1, 1, 1);
 
   // Check operator constraint for number of arguments
   static_assert(check_operator_constraints(std::layout_right::mapping<std::extents<int, D>>(std::extents<int, D>(1)), 0));
diff --git a/libcxx/test/std/containers/views/mdspan/layout_right/properties.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_right/properties.pass.cpp
index 26eb2e0fe6561..e10e073c8fb13 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_right/properties.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_right/properties.pass.cpp
@@ -53,7 +53,7 @@ constexpr void test_layout_mapping_right() {
 constexpr bool test() {
   constexpr size_t D = std::dynamic_extent;
   test_layout_mapping_right<std::extents<int>>();
-  test_layout_mapping_right<std::extents<char, 4, 5>>();
+  test_layout_mapping_right<std::extents<signed char, 4, 5>>();
   test_layout_mapping_right<std::extents<unsigned, D, 4>>();
   test_layout_mapping_right<std::extents<size_t, D, D, D, D>>();
   return true;
diff --git a/libcxx/test/std/containers/views/mdspan/layout_right/static_requirements.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_right/static_requirements.pass.cpp
index d460f1a5dbc46..c4e3d89cb94f4 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_right/static_requirements.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_right/static_requirements.pass.cpp
@@ -124,7 +124,7 @@ void test_layout_mapping_right() {
 int main(int, char**) {
   constexpr size_t D = std::dynamic_extent;
   test_layout_mapping_right<std::extents<int>>();
-  test_layout_mapping_right<std::extents<char, 4, 5>>();
+  test_layout_mapping_right<std::extents<signed char, 4, 5>>();
   test_layout_mapping_right<std::extents<unsigned, D, 4>>();
   test_layout_mapping_right<std::extents<size_t, D, D, D, D>>();
   return 0;
diff --git a/libcxx/test/std/containers/views/mdspan/layout_stride/extents.verify.cpp b/libcxx/test/std/containers/views/mdspan/layout_stride/extents.verify.cpp
index 46f2b774bcbd9..0c2ec888ab35b 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_stride/extents.verify.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_stride/extents.verify.cpp
@@ -29,5 +29,5 @@ void not_extents() {
 
 void representable() {
   // expected-error-re@*:* {{static assertion failed {{.*}}layout_stride::mapping product of static extents must be representable as index_type.}}
-  [[maybe_unused]] std::layout_stride::mapping<std::extents<char, 20, 20>> mapping;
+  [[maybe_unused]] std::layout_stride::mapping<std::extents<signed char, 20, 20>> mapping;
 }
diff --git a/libcxx/test/std/containers/views/mdspan/layout_stride/index_operator.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_stride/index_operator.pass.cpp
index dbd56a54758c9..01278e9076714 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_stride/index_operator.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_stride/index_operator.pass.cpp
@@ -79,7 +79,7 @@ constexpr bool test() {
   test_iteration<std::extents<unsigned, D>>(std::array<int, 1>{3}, 7);
   test_iteration<std::extents<unsigned, 7>>(std::array<int, 1>{4});
   test_iteration<std::extents<unsigned, 7, 8>>(std::array<int, 2>{25, 3});
-  test_iteration<std::extents<char, D, D, D, D>>(std::array<int, 4>{1, 1, 1, 1}, 1, 1, 1, 1);
+  test_iteration<std::extents<signed char, D, D, D, D>>(std::array<int, 4>{1, 1, 1, 1}, 1, 1, 1, 1);
 
   // Check operator constraint for number of arguments
   static_assert(check_operator_constraints(
diff --git a/libcxx/test/std/containers/views/mdspan/layout_stride/properties.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_stride/properties.pass.cpp
index d3d0aa6b3c3a5..8dba35cd9d336 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_stride/properties.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_stride/properties.pass.cpp
@@ -102,8 +102,8 @@ test_layout_mapping_stride(E ext, std::array<typename E::index_type, E::rank()>
 constexpr bool test() {
   constexpr size_t D = std::dynamic_extent;
   test_layout_mapping_stride(std::extents<int>(), std::array<int, 0>{}, true);
-  test_layout_mapping_stride(std::extents<char, 4, 5>(), std::array<char, 2>{1, 4}, true);
-  test_layout_mapping_stride(std::extents<char, 4, 5>(), std::array<char, 2>{1, 5}, false);
+  test_layout_mapping_stride(std::extents<signed char, 4, 5>(), std::array<signed char, 2>{1, 4}, true);
+  test_layout_mapping_stride(std::extents<signed char, 4, 5>(), std::array<signed char, 2>{1, 5}, false);
   test_layout_mapping_stride(std::extents<unsigned, D, 4>(7), std::array<unsigned, 2>{20, 2}, false);
   test_layout_mapping_stride(std::extents<size_t, D, D, D, D>(3, 3, 3, 3), std::array<size_t, 4>{3, 1, 9, 27}, true);
   return true;
diff --git a/libcxx/test/std/containers/views/mdspan/layout_stride/static_requirements.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_stride/static_requirements.pass.cpp
index b56d0087260d1..8c5bf16b37c1e 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_stride/static_requirements.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_stride/static_requirements.pass.cpp
@@ -124,7 +124,7 @@ void test_layout_mapping_stride() {
 int main(int, char**) {
   constexpr size_t D = std::dynamic_extent;
   test_layout_mapping_stride<std::extents<int>>();
-  test_layout_mapping_stride<std::extents<char, 4, 5>>();
+  test_layout_mapping_stride<std::extents<signed char, 4, 5>>();
   test_layout_mapping_stride<std::extents<unsigned, D, 4>>();
   test_layout_mapping_stride<std::extents<size_t, D, D, D, D>>();
   return 0;
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/assign.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/assign.pass.cpp
index 8741c79315f1e..b282277d0dc06 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/assign.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/assign.pass.cpp
@@ -57,10 +57,10 @@ template <class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.copy.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.copy.pass.cpp
index 7fb85ed845d6c..75f2fc3dd603a 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.copy.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.copy.pass.cpp
@@ -47,10 +47,10 @@ template <class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.default.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.default.pass.cpp
index 8ad12944df84d..5c0ae126dff24 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.default.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.default.pass.cpp
@@ -59,10 +59,10 @@ template <bool hc, bool mc, bool ac, class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types<hc, mc, ac>(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types<hc, mc, ac>(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types<hc, mc, ac>(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types<hc, mc, ac>(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types<hc, mc, ac>(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types<hc, mc, ac>(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types<hc, mc, ac>(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types<hc, mc, ac>(
       handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
@@ -74,8 +74,8 @@ constexpr void mixin_layout(const H& handle, const A& acc) {
 
   // Use weird layout, make sure it has the properties we want to test
   constexpr size_t D = std::dynamic_extent;
-  static_assert(
-      !std::is_default_constructible_v< typename layout_wrapping_integral<4>::template mapping<std::extents<char, D>>>);
+  static_assert(!std::is_default_constructible_v<
+                typename layout_wrapping_integral<4>::template mapping<std::extents<signed char, D>>>);
   mixin_extents<hc, false, ac>(handle, layout_wrapping_integral<4>(), acc);
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_array.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_array.pass.cpp
index 3c8797c023e1b..2e5c842b50d45 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_array.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_array.pass.cpp
@@ -105,10 +105,10 @@ template <bool mec, bool ac, class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_ctor<mec, ac>(
       handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_extents.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_extents.pass.cpp
index 37ee8bdc2e1af..007ab9cdc636d 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_extents.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_extents.pass.cpp
@@ -68,10 +68,10 @@ template <bool mec, bool ac, class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types<mec, ac>(
       handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_integers.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_integers.pass.cpp
index f4a3e8adc40d8..985a8911e15b6 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_integers.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_integers.pass.cpp
@@ -84,17 +84,17 @@ constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   // construct from just dynamic extents
   test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<char, D>(7)), acc, 7);
+  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc, 7);
   test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc, 2, 3);
-  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc, 0, 3);
+  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc, 0, 3);
   test_mdspan_types<mec, ac>(
       handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc, 1, 2, 3, 2);
 
   // construct from all extents
   test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc, 7);
   test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc, 2, 4, 3);
-  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc, 0, 7, 3);
+  test_mdspan_types<mec, ac>(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc, 0, 7, 3);
   test_mdspan_types<mec, ac>(
       handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc, 1, 7, 2, 4, 3, 2);
 }
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_map.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_map.pass.cpp
index 995bc5d6d1181..4c636255c1c78 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_map.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_map.pass.cpp
@@ -65,10 +65,10 @@ template <bool ac, class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types<ac>(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types<ac>(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types<ac>(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types<ac>(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types<ac>(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types<ac>(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types<ac>(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types<ac>(handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_map_acc.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_map_acc.pass.cpp
index c2d76a47b2ee1..76ca7810963df 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_map_acc.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_map_acc.pass.cpp
@@ -57,10 +57,10 @@ template <class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_span.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_span.pass.cpp
index 7084e626171d4..ad4da40630c97 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_span.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.dh_span.pass.cpp
@@ -105,10 +105,10 @@ template <bool mec, bool ac, class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_ctor<mec, ac>(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_ctor<mec, ac>(
       handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.move.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.move.pass.cpp
index 10bd5114bd4d8..a65d0f4484178 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/ctor.move.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/ctor.move.pass.cpp
@@ -46,10 +46,10 @@ template <class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/deduction.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/deduction.pass.cpp
index d83299c2c53c9..557829dcbad9b 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/deduction.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/deduction.pass.cpp
@@ -80,10 +80,10 @@ template <class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/index_operator.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/index_operator.pass.cpp
index 5af2b3a45874b..2b843d6e4eb8e 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/index_operator.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/index_operator.pass.cpp
@@ -120,7 +120,7 @@ constexpr void test_layout() {
   test_iteration(construct_mapping(Layout(), std::extents<unsigned, D>(7)));
   test_iteration(construct_mapping(Layout(), std::extents<unsigned, 7>()));
   test_iteration(construct_mapping(Layout(), std::extents<unsigned, 7, 8>()));
-  test_iteration(construct_mapping(Layout(), std::extents<char, D, D, D, D>(1, 1, 1, 1)));
+  test_iteration(construct_mapping(Layout(), std::extents<signed char, D, D, D, D>(1, 1, 1, 1)));
 
 // TODO enable for GCC 13, when the CI pipeline is switched, doesn't work with GCC 12
 #if defined(__clang_major__) && __clang_major__ >= 17
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/move.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/move.pass.cpp
index 4729bd171da86..1c5f404d49fb2 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/move.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/move.pass.cpp
@@ -49,10 +49,10 @@ template <class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/properties.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/properties.pass.cpp
index 8f2bc42c8c01e..35534fa879548 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/properties.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/properties.pass.cpp
@@ -178,10 +178,10 @@ template <class H, class L, class A>
 constexpr void mixin_extents(const H& handle, const L& layout, const A& acc) {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int>()), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D>(7)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D>(7)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<unsigned, 7>()), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<size_t, D, 4, D>(2, 3)), acc);
-  test_mdspan_types(handle, construct_mapping(layout, std::extents<char, D, 7, D>(0, 3)), acc);
+  test_mdspan_types(handle, construct_mapping(layout, std::extents<signed char, D, 7, D>(0, 3)), acc);
   test_mdspan_types(handle, construct_mapping(layout, std::extents<int64_t, D, 7, D, 4, D, D>(1, 2, 3, 2)), acc);
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/mdspan/types.pass.cpp b/libcxx/test/std/containers/views/mdspan/mdspan/types.pass.cpp
index 2dea5a82b6516..7e0235105b0b1 100644
--- a/libcxx/test/std/containers/views/mdspan/mdspan/types.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/mdspan/types.pass.cpp
@@ -136,9 +136,9 @@ template <class T, class L, class A>
 void mixin_extents() {
   constexpr size_t D = std::dynamic_extent;
   test_mdspan_types<T, std::extents<int>, L, A>();
-  test_mdspan_types<T, std::extents<char, D>, L, A>();
-  test_mdspan_types<T, std::dextents<char, 7>, L, A>();
-  test_mdspan_types<T, std::dextents<char, 9>, L, A>();
+  test_mdspan_types<T, std::extents<signed char, D>, L, A>();
+  test_mdspan_types<T, std::dextents<signed char, 7>, L, A>();
+  test_mdspan_types<T, std::dextents<signed char, 9>, L, A>();
   test_mdspan_types<T, std::extents<unsigned, 7>, L, A>();
   test_mdspan_types<T, std::extents<unsigned, D, D, D>, L, A>();
   test_mdspan_types<T, std::extents<size_t, D, 7, D>, L, A>();