[gcc(refs/users/aoliva/heads/testme)] hash set: reject attempts to insert null pointers

[Alexandre Oliva <aoliva@gcc.gnu.org>]

https://gcc.gnu.org/g:3634f8ee967c3adb60efc759f9aca885b83ba2bc

commit 3634f8ee967c3adb60efc759f9aca885b83ba2bc
Author: Alexandre Oliva <oliva@gnu.org>
Date:   Thu Dec 22 21:28:48 2022 -0300

    hash set: reject attempts to insert null pointers

Diff:
---
 gcc/hash-set.h | 6 +++++-
 gcc/varpool.cc | 4 +++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/gcc/hash-set.h b/gcc/hash-set.h
index 76fa7f39456..a98121a060e 100644
--- a/gcc/hash-set.h
+++ b/gcc/hash-set.h
@@ -58,7 +58,11 @@ public:
       Key *e = m_table.find_slot_with_hash (k, Traits::hash (k), INSERT);
       bool existed = !Traits::is_empty (*e);
       if (!existed)
-	new (e) Key (k);
+	{
+	  new (e) Key (k);
+	  // Catch attempts to insert e.g. a NULL pointer.
+	  gcc_checking_assert (!Traits::is_empty (*e));
+	}
 
       return existed;
     }
diff --git a/gcc/varpool.cc b/gcc/varpool.cc
index bfd17f1250c..ccbd6e50f4b 100644
--- a/gcc/varpool.cc
+++ b/gcc/varpool.cc
@@ -680,10 +680,12 @@ symbol_table::remove_unreferenced_decls (void)
 	    enqueue_node (vnode, &first);
 	  else
 	    {
-	      referenced.add (vnode);
+	      if (vnode)
+		referenced.add (vnode);
 	      while (vnode && vnode->alias && vnode->definition)
 		{
 		  vnode = vnode->get_alias_target ();
+		  gcc_checking_assert (vnode);
 	          referenced.add (vnode);
 		}
 	    }