From 0b786ff38ab398087820d91241e030a28c451df9 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Thu, 1 Feb 2024 16:54:39 -0500
Subject: [PATCH] c++: variable template array of unknown bound [PR113638]

When we added variable templates, we didn't extend the VAR_HAD_UNKNOWN_BOUND
handling for class template static data members to handle them as well.

	PR c++/113638

gcc/cp/ChangeLog:

	* cp-tree.h: Adjust comment.
	* pt.cc (instantiate_template): Set VAR_HAD_UNKNOWN_BOUND for
	variable template.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1y/var-templ-array1.C: New test.
---
 gcc/cp/cp-tree.h                              |  2 +-
 gcc/cp/pt.cc                                  | 13 ++++++++++---
 gcc/testsuite/g++.dg/cpp1y/var-templ-array1.C |  7 +++++++
 3 files changed, 18 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/var-templ-array1.C

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index f46b448ce0d..969c7239c97 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -3251,7 +3251,7 @@ struct GTY(()) lang_decl {
 #define DECL_CONV_FN_TYPE(FN) \
   TREE_TYPE ((gcc_checking_assert (DECL_CONV_FN_P (FN)), DECL_NAME (FN)))
 
-/* Nonzero if NODE, a static data member, was declared in its class as an
+/* Nonzero if NODE, a templated variable, was declared as an
    array of unknown bound.  */
 #define VAR_HAD_UNKNOWN_BOUND(NODE)			\
   (DECL_LANG_SPECIFIC (VAR_DECL_CHECK (NODE))		\
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 16febb1ba7f..9d30a271713 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -22105,9 +22105,16 @@ instantiate_template (tree tmpl, tree orig_args, tsubst_flags_t complain)
   DECL_TI_TEMPLATE (fndecl) = tmpl;
   DECL_TI_ARGS (fndecl) = targ_ptr;
   if (VAR_P (pattern))
-    /* Now that we we've formed this variable template specialization,
-       remember the result of most_specialized_partial_spec for it.  */
-    TI_PARTIAL_INFO (DECL_TEMPLATE_INFO (fndecl)) = partial_ti;
+    {
+      /* Now that we we've formed this variable template specialization,
+	 remember the result of most_specialized_partial_spec for it.  */
+      TI_PARTIAL_INFO (DECL_TEMPLATE_INFO (fndecl)) = partial_ti;
+
+      /* And remember if the variable was declared with [].  */
+      if (TREE_CODE (TREE_TYPE (fndecl)) == ARRAY_TYPE
+	  && TYPE_DOMAIN (TREE_TYPE (fndecl)) == NULL_TREE)
+	SET_VAR_HAD_UNKNOWN_BOUND (fndecl);
+    }
 
   fndecl = register_specialization (fndecl, gen_tmpl, targ_ptr, false, hash);
   if (fndecl == error_mark_node)
diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ-array1.C b/gcc/testsuite/g++.dg/cpp1y/var-templ-array1.C
new file mode 100644
index 00000000000..b0ff7e74556
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/var-templ-array1.C
@@ -0,0 +1,7 @@
+// PR c++/113638
+// { dg-do compile { target c++14 } }
+
+template<int ...Is>
+constexpr int my_array[]{Is...};
+constexpr auto t1 = my_array<2>;
+static_assert(sizeof(my_array<1>) == sizeof(int) * 1, "");