From 98d302bab9a87d3f2daecf9d54d62f33ba216673 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Arsen=20Arsenovi=C4=87?= <arsen@aarsen.me>
Date: Wed, 8 Mar 2023 17:01:24 +0100
Subject: [PATCH 2/4] libstdc++: Add a test for <version> FTM redefinitions

This test detects redefinitions by compiling stdc++.h with
-Wsystem-headers.  Thanks Patrick Palka for the suggestion.

libstdc++-v3/ChangeLog:

	* testsuite/17_intro/versionconflict.cc: New test.
---
 libstdc++-v3/include/std/version                   | 5 ++++-
 libstdc++-v3/testsuite/17_intro/versionconflict.cc | 7 +++++++
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 libstdc++-v3/testsuite/17_intro/versionconflict.cc

diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index cdd24248c57..1069bc6c9f6 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -30,7 +30,10 @@
 #ifndef _GLIBCXX_VERSION_INCLUDED
 #define _GLIBCXX_VERSION_INCLUDED
 
-#pragma GCC system_header
+// To facilitate testsuite/17_intro/versionconflict.cc
+#ifndef _GLIBCXX_TESTING_SYSHDR
+# pragma GCC system_header
+#endif
 
 #include <bits/c++config.h>
 
diff --git a/libstdc++-v3/testsuite/17_intro/versionconflict.cc b/libstdc++-v3/testsuite/17_intro/versionconflict.cc
new file mode 100644
index 00000000000..6c212980ab0
--- /dev/null
+++ b/libstdc++-v3/testsuite/17_intro/versionconflict.cc
@@ -0,0 +1,7 @@
+// { dg-do preprocess }
+// { dg-additional-options "-Werror" }
+
+// Test for redefinitions of FTMs using bits/stdc++.h.
+#define _GLIBCXX_TESTING_SYSHDR
+#include <bits/stdc++.h>
+#include <version>
-- 
2.40.0