[PATCH v2 1/5] libstdc++: Check prerequisites of layout_*::operator().

[Luc Grosheintz]

Previously the prerequisite that the arguments passed to operator() are
a multi-dimensional index (of extents()) was not checked.

This commit adds the __glibcxx_asserts and the required tests.

libstdc++-v3/ChangeLog:

        * include/std/mdspan: Check prerequisites of
        layout_*::operator().
        * testsuite/23_containers/mdspan/layouts/class_mandate_neg.cc:
        Add tests for prerequisites.

Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
---
 libstdc++-v3/include/std/mdspan               |  4 +++
 .../mdspan/layouts/class_mandate_neg.cc       | 26 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index c72a64094b7..39d02ac08df 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -441,6 +441,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
            _IndexType __mult = 1;
            auto __update = [&, __pos = 0u](_IndexType __idx) mutable
              {
+               __glibcxx_assert(cmp_less(__idx, __exts.extent(__pos)));
                __res += __idx * __mult;
                __mult *= __exts.extent(__pos);
                ++__pos;
@@ -651,6 +652,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
            auto __update = [&, __pos = __exts.rank()](_IndexType) mutable
              {
                --__pos;
+               __glibcxx_assert(cmp_less(__ind_arr[__pos],
+                                         __exts.extent(__pos)));
                __res += __ind_arr[__pos] * __mult;
                __mult *= __exts.extent(__pos);
              };
@@ -822,6 +825,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
          {
            auto __update = [&, __pos = 0u](_IndexType __idx) mutable
              {
+               __glibcxx_assert(cmp_less(__idx, __m.extents().extent(__pos)));
                __res += __idx * __m.stride(__pos++);
              };
            (__update(__indices), ...);
diff --git 
a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/class_mandate_neg.cc 
b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/class_mandate_neg.cc
index 7091153daba..f5aab22aff0 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/class_mandate_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/class_mandate_neg.cc
@@ -45,4 +45,30 @@ auto b5 = B<5, std::layout_stride, std::layout_right>();  // 
{ dg-error "require
 auto b6 = B<6, std::layout_stride, std::layout_left>();   // { dg-error 
"required from" }
 auto b7 = B<7, std::layout_stride, std::layout_stride>(); // { dg-error 
"required from" }
 
+template<typename Layout>
+  constexpr bool
+  test_linear_index_0d()
+  {
+    auto m = typename Layout::mapping<std::extents<int, 0>>{};
+    (void) m(0); // { dg-error "expansion of" }
+    return true;
+  }
+static_assert(test_linear_index_0d<std::layout_left>()); // { dg-error 
"expansion of" }
+static_assert(test_linear_index_0d<std::layout_right>()); // { dg-error 
"expansion of" }
+static_assert(test_linear_index_0d<std::layout_stride>()); // { dg-error 
"expansion of" }
+
+template<typename Layout>
+  constexpr bool
+  test_linear_index_3d()
+  {
+    auto m = typename Layout::mapping<std::extents<int, 3, 5, 7>>{};
+    (void) m(2, 5, 5); // { dg-error "expansion of" }
+    return true;
+  }
+static_assert(test_linear_index_3d<std::layout_left>()); // { dg-error 
"expansion of" }
+static_assert(test_linear_index_3d<std::layout_right>()); // { dg-error 
"expansion of" }
+static_assert(test_linear_index_3d<std::layout_stride>()); // { dg-error 
"expansion of" }
+
 // { dg-prune-output "must be representable as index_type" }
+// { dg-prune-output "non-constant condition for static assertion" }
+// { dg-prune-output "__glibcxx_assert" }
-- 
2.49.0