[Bug libstdc++/58876] No non-virtual-dtor warning in std::unique_ptr

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58876

--- Comment #15 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This seems simpler and cleaner:

--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -5244,6 +5244,10 @@ build_delete (location_t loc, tree otype, tree addr,
              tree dtor = CLASSTYPE_DESTRUCTOR (type);
              if (!dtor || !DECL_VINDEX (dtor))
                {
+                 const bool prev = global_dc->m_warn_system_headers;
+                 // Don't suppress this warning in system headers.
+                 global_dc->m_warn_system_headers = true;
+
                  if (CLASSTYPE_PURE_VIRTUALS (type))
                    warning_at (loc, OPT_Wdelete_non_virtual_dtor,
                                "deleting object of abstract class type %qT"
@@ -5254,6 +5258,7 @@ build_delete (location_t loc, tree otype, tree addr,
                                "deleting object of polymorphic class type %qT"
                                " which has non-virtual destructor"
                                " might cause undefined behavior", type);
+                 global_dc->m_warn_system_headers = prev;
                }
            }
        }

This warning is always useful, even in system headers.

But Jason is working on an ever better solution, so that we can stop using the
system_header pragma in libstdc++ headers.