From 37e6c9bd99575752b7122c5d76aa2cf021deb93c Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Fri, 17 Nov 2023 21:57:52 -0500
Subject: c++: mangling for CTAD placeholder

Per https://github.com/itanium-cxx-abi/cxx-abi/issues/109 mangle a C++17
CTAD placeholder as its template.

gcc/cp/ChangeLog:

	* mangle.cc (write_type): Mangle placeholder as its template.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/nontype-class4.C: Specify ABI v18.
	* g++.dg/cpp2a/nontype-class4a.C: New test.
---
 gcc/cp/mangle.cc | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'gcc/cp/mangle.cc')

diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc
index 8a44b11..0684f0e 100644
--- a/gcc/cp/mangle.cc
+++ b/gcc/cp/mangle.cc
@@ -2539,6 +2539,16 @@ write_type (tree type)
 	    case TEMPLATE_TYPE_PARM:
 	      if (is_auto (type))
 		{
+		  if (template_placeholder_p (type)
+		      && abi_check (19))
+		    {
+		      /* ABI #109: placeholder is mangled as its template.  */
+		      type = CLASS_PLACEHOLDER_TEMPLATE (type);
+		      if (find_substitution (type))
+			return;
+		      write_name (type, 0);
+		      break;
+		    }
 		  if (AUTO_IS_DECLTYPE (type))
 		    write_identifier ("Dc");
 		  else
-- 
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