[gcc r15-10340] libstdc++: Explicitly pass -Wsystem-headers in tests that need it

[Patrick Palka]

https://gcc.gnu.org/g:2da81100da46ad89ec8c2dacca8a20632aa1c5de

commit r15-10340-g2da81100da46ad89ec8c2dacca8a20632aa1c5de
Author: Patrick Palka <ppalka@redhat.com>
Date:   Tue Sep 16 20:59:10 2025 -0400

    libstdc++: Explicitly pass -Wsystem-headers in tests that need it
    
    When running libstdc++ tests using an installed gcc (as opposed to an
    in-tree gcc), we naturally use system stdlib headers instead of the
    in-tree headers.  But warnings from within system headers are suppressed
    by default, so tests that check for such warnings spuriously fail in such
    a setup.  This patch makes us compile such tests with -Wsystem-headers so
    that they consistently pass.
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/20_util/bind/dangling_ref.cc: Compile with
            -Wsystem-headers.
            * testsuite/20_util/ratio/operations/ops_overflow_neg.cc: Likewise.
            * testsuite/20_util/unique_ptr/lwg4148.cc: Likewise.
            * testsuite/29_atomics/atomic/operators/pointer_partial_void.cc:
            Likewise.
            * testsuite/30_threads/packaged_task/cons/dangling_ref.cc:
            Likewise.
    
    Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
    (cherry picked from commit e690b97761e18daccb4fff0151c97c1d0115b55f)

Diff:
---
 libstdc++-v3/testsuite/20_util/bind/dangling_ref.cc                     | 1 +
 libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc     | 2 +-
 libstdc++-v3/testsuite/20_util/unique_ptr/lwg4148.cc                    | 1 +
 .../testsuite/29_atomics/atomic/operators/pointer_partial_void.cc       | 1 +
 libstdc++-v3/testsuite/30_threads/packaged_task/cons/dangling_ref.cc    | 1 +
 5 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/testsuite/20_util/bind/dangling_ref.cc b/libstdc++-v3/testsuite/20_util/bind/dangling_ref.cc
index 17e7b21c45cb..32af0a27b8fe 100644
--- a/libstdc++-v3/testsuite/20_util/bind/dangling_ref.cc
+++ b/libstdc++-v3/testsuite/20_util/bind/dangling_ref.cc
@@ -1,4 +1,5 @@
 // { dg-do compile { target c++11 } }
+// { dg-additional-options "-Wsystem-headers" }
 #include <functional>
 
 int f();
diff --git a/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc b/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc
index 5eff8e31f82a..368866a63313 100644
--- a/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/ratio/operations/ops_overflow_neg.cc
@@ -1,6 +1,6 @@
 // { dg-do compile { target c++11 } }
 // { dg-require-cstdint "" }
-
+// { dg-additional-options "-Wsystem-headers" }
 // 2008-07-03 Chris Fairles <chris.fairles@gmail.com>
 
 // Copyright (C) 2008-2025 Free Software Foundation, Inc.
diff --git a/libstdc++-v3/testsuite/20_util/unique_ptr/lwg4148.cc b/libstdc++-v3/testsuite/20_util/unique_ptr/lwg4148.cc
index c70d7a60631b..f5697e4e4021 100644
--- a/libstdc++-v3/testsuite/20_util/unique_ptr/lwg4148.cc
+++ b/libstdc++-v3/testsuite/20_util/unique_ptr/lwg4148.cc
@@ -1,4 +1,5 @@
 // { dg-do compile { target c++11 } }
+// { dg-additional-options "-Wsystem-headers" }
 
 // LWG 4148. unique_ptr::operator* should not allow dangling references
 
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/operators/pointer_partial_void.cc b/libstdc++-v3/testsuite/29_atomics/atomic/operators/pointer_partial_void.cc
index e959418a1c3c..1e2f71e9c628 100644
--- a/libstdc++-v3/testsuite/29_atomics/atomic/operators/pointer_partial_void.cc
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/operators/pointer_partial_void.cc
@@ -1,6 +1,7 @@
 // { dg-do run { target { c++11_only || c++14_only } } }
 // { dg-require-atomic-builtins "" }
 // { dg-require-effective-target hosted }
+// { dg-additional-options "-Wsystem-headers" }
 
 // Copyright (C) 2012-2025 Free Software Foundation, Inc.
 //
diff --git a/libstdc++-v3/testsuite/30_threads/packaged_task/cons/dangling_ref.cc b/libstdc++-v3/testsuite/30_threads/packaged_task/cons/dangling_ref.cc
index 51c6ade91c36..83411c7024e9 100644
--- a/libstdc++-v3/testsuite/30_threads/packaged_task/cons/dangling_ref.cc
+++ b/libstdc++-v3/testsuite/30_threads/packaged_task/cons/dangling_ref.cc
@@ -1,4 +1,5 @@
 // { dg-do compile { target c++11 } }
+// { dg-additional-options "-Wsystem-headers" }
 #include <future>
 
 // C++20 [futures.task.members]