[gcc r14-6188] libstdc++: Add test for LWG Issue 3897

[Jonathan Wakely]

https://gcc.gnu.org/g:9fff752695648b06a977b046990d69d41a1bf702

commit r14-6188-g9fff752695648b06a977b046990d69d41a1bf702
Author: Will Hawkins <hawkinsw@obs.cr>
Date:   Mon Dec 4 20:59:44 2023 +0000

    libstdc++: Add test for LWG Issue 3897
    
    Add a test to verify that the implementation of inout_ptr is not
    vulnerable to LWG Issue 3897.
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/20_util/smartptr.adapt/inout_ptr/2.cc: Add check
            for LWG Issue 3897.
    
    Co-authored-by: Jonathan Wakely <jwakely@redhat.com>

Diff:
---
 .../testsuite/20_util/smartptr.adapt/inout_ptr/2.cc       | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/libstdc++-v3/testsuite/20_util/smartptr.adapt/inout_ptr/2.cc b/libstdc++-v3/testsuite/20_util/smartptr.adapt/inout_ptr/2.cc
index ca6076209c2..b4a2d95227a 100644
--- a/libstdc++-v3/testsuite/20_util/smartptr.adapt/inout_ptr/2.cc
+++ b/libstdc++-v3/testsuite/20_util/smartptr.adapt/inout_ptr/2.cc
@@ -96,7 +96,22 @@ test_unique_ptr()
   VERIFY( upbd->id == 2 );
 }
 
+void
+test_lwg3897()
+{
+  // Verify that implementation handles LWG Issue 3897
+  auto nuller = [](int** p) {
+    delete *p;
+    *p = nullptr;
+  };
+  int* i = new int{5};
+  nuller(std::inout_ptr(i));
+
+  VERIFY( i == nullptr );
+}
+
 int main()
 {
   test_unique_ptr();
+  test_lwg3897();
 }