1 files changed, 26 insertions, 0 deletions
diff --git a/test/SemaCXX/constexpr-array-unknown-bound.cpp b/test/SemaCXX/constexpr-array-unknown-bound.cpp
new file mode 100644
index 0000000000000..395c4cbd127b2
--- /dev/null
+++ b/test/SemaCXX/constexpr-array-unknown-bound.cpp
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 %s -Wno-uninitialized -std=c++1z -fsyntax-only -verify
+
+const extern int arr[];
+constexpr auto p = arr; // ok
+constexpr int f(int i) {return p[i];} // expected-note {{read of dereferenced one-past-the-end pointer}}
+
+constexpr int arr[] {1, 2, 3};
+constexpr auto p2 = arr + 2; // ok
+constexpr int x = f(2); // ok
+constexpr int y = f(3); // expected-error {{constant expression}}
+// expected-note-re@-1 {{in call to 'f({{.*}})'}}
+
+// FIXME: consider permitting this case
+struct A {int m[];} a;
+constexpr auto p3 = a.m; // expected-error {{constant expression}} expected-note {{without known bound}}
+constexpr auto p4 = a.m + 1; // expected-error {{constant expression}} expected-note {{without known bound}}
+
+void g(int i) {
+  int arr[i];
+  constexpr auto *p = arr + 2; // expected-error {{constant expression}} expected-note {{without known bound}}
+
+  // FIXME: Give a better diagnostic here. The issue is that computing
+  // sizeof(*arr2) within the array indexing fails due to the VLA.
+  int arr2[2][i];
+  constexpr int m = ((void)arr2[2], 0); // expected-error {{constant expression}}
+}