From f620e64a6f13371b95be5b17abba0acf15bf7cae Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Thu, 29 Oct 2020 15:08:31 -0400
Subject: [PATCH] c++: Disable -Winit-list-lifetime in unevaluated operand
 [PR97632]

Jon suggested turning this warning off when we're not actually
evaluating the operand.  This patch does that.

gcc/cp/ChangeLog:

	PR c++/97632
	* init.c (build_new_1): Disable -Winit-list-lifetime for an unevaluated
	operand.

gcc/testsuite/ChangeLog:

	PR c++/97632
	* g++.dg/warn/Winit-list4.C: New test.
---
 gcc/cp/init.c                           |  2 +-
 gcc/testsuite/g++.dg/warn/Winit-list4.C | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/warn/Winit-list4.C

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 1bddb6555dc..ffb84ea5b09 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -2957,7 +2957,7 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
       return error_mark_node;
     }
 
-  if (is_std_init_list (elt_type))
+  if (is_std_init_list (elt_type) && !cp_unevaluated_operand)
     warning (OPT_Winit_list_lifetime,
 	     "%<new%> of %<initializer_list%> does not "
 	     "extend the lifetime of the underlying array");
diff --git a/gcc/testsuite/g++.dg/warn/Winit-list4.C b/gcc/testsuite/g++.dg/warn/Winit-list4.C
new file mode 100644
index 00000000000..d136187e2c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Winit-list4.C
@@ -0,0 +1,15 @@
+// PR c++/97632
+// { dg-do compile { target c++20 } }
+// Test we don't warn in an unevaluated operand.
+
+#include <initializer_list>
+
+template<typename _Tp>
+concept default_initializable
+  = requires
+    {
+      _Tp{};
+      (void) ::new _Tp; // { dg-bogus "does not extend the lifetime" }
+    };
+
+static_assert(default_initializable<std::initializer_list<int>>);
-- 
2.30.2