[libc++] Fix PR35491 - std::array of zero-size doesn't work with non-default constructible types.

Summary:
This patch fixes llvm.org/PR35491 and LWG2157  (https://cplusplus.github.io/LWG/issue2157)

The fix attempts to maintain ABI compatibility by replacing the array with a instance of `aligned_storage`.

Reviewers: mclow.lists, EricWF

Reviewed By: EricWF

Subscribers: lichray, cfe-commits

Differential Revision: https://reviews.llvm.org/D41223

llvm-svn: 324526

1 files changed, 10 insertions, 0 deletions

diff --git a/libcxx/test/std/containers/sequences/array/begin.pass.cpp b/libcxx/test/std/containers/sequences/array/begin.pass.cpp
index b12ffc851b8..282a947fefe 100644
--- a/libcxx/test/std/containers/sequences/array/begin.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/begin.pass.cpp
@@ -18,6 +18,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
+
 int main()
 {
     {
@@ -31,4 +32,13 @@ int main()
         *i = 5.5;
         assert(c[0] == 5.5);
     }
+    {
+      struct NoDefault {
+        NoDefault(int) {}
+      };
+      typedef NoDefault T;
+      typedef std::array<T, 0> C;
+      C c = {};
+      assert(c.begin() == c.end());
+    }
 }