From 054aeaef276572c2ccbedbd7aa86046be338603c Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Mon, 2 Mar 2020 14:42:47 -0500
Subject: [PATCH] c++: Fix ({ ... }) array mem-initializer.

Here, we were going down the wrong path in perform_member_init because of
the incorrect parens around the mem-initializer for the array.  And then
cxx_eval_vec_init_1 didn't know what to do with a CONSTRUCTOR as the
initializer.  For GCC 9, let's just fix the latter issue.

gcc/cp/ChangeLog
2020-03-02  Jason Merrill  <jason@redhat.com>

	PR c++/86917
	* constexpr.c (cxx_eval_vec_init_1): Handle CONSTRUCTOR.
---
 gcc/cp/ChangeLog                              |  5 ++++
 gcc/cp/constexpr.c                            |  4 ++++
 .../g++.dg/cpp0x/constexpr-array23.C          | 24 +++++++++++++++++++
 3 files changed, 33 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-array23.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 7692a8f1903f..614844ef9061 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2020-03-02  Jason Merrill  <jason@redhat.com>
+
+	PR c++/86917
+	* constexpr.c (cxx_eval_vec_init_1): Handle CONSTRUCTOR.
+
 2020-03-02  Jason Merrill  <jason@redhat.com>
 
 	PR c++/91953
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 2006ad9f45ee..8fd5e4f2126a 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -3135,6 +3135,10 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree atype, tree init,
   unsigned HOST_WIDE_INT i;
   tsubst_flags_t complain = ctx->quiet ? tf_none : tf_warning_or_error;
 
+  if (init && TREE_CODE (init) == CONSTRUCTOR)
+    return cxx_eval_bare_aggregate (ctx, init, lval,
+				    non_constant_p, overflow_p);
+
   /* For the default constructor, build up a call to the default
      constructor of the element type.  We only need to handle class types
      here, as for a constructor to be constexpr, all members must be
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-array23.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-array23.C
new file mode 100644
index 000000000000..e94695efa2ae
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-array23.C
@@ -0,0 +1,24 @@
+// PR c++/86917
+// { dg-do compile { target c++11 } }
+
+struct A
+{
+  constexpr A () : c (0) {}
+  static const A z;
+  unsigned c;
+};
+
+struct B
+{				// This should really be target { ! c++2a }
+  typedef A W[4];		// { dg-error "paren" "" { xfail *-*-* } .+1 }
+  constexpr B () : w ({ A::z, A::z, A::z, A::z }) {} // { dg-error "constant" "" { xfail *-*-* } }
+  W w;
+};
+
+struct C
+{
+  C ();
+  B w[1];
+};
+
+C::C () { }
-- 
2.47.2