c++/modules: Fix merging of GM entities in partitions [PR114950]

Currently name lookup generally seems to assume that all entities
declared within a named module (partition) are attached to said module,
which is not true for GM entities (e.g. via extern "C++"), and causes
issues with deduplication.

This patch fixes the issue by ensuring that module attachment of a
declaration is consistently used to handling merging.  Handling this
exposes some issues with deduplicating temploid friends; to resolve this
we always create the BINDING_SLOT_PARTITION slot so that we have
somewhere to place attached names (from any module).

This doesn't yet completely handle issues with allowing otherwise
conflicting temploid friends from different modules to co-exist in the
same module if neither are reachable from the other via name lookup.

	PR c++/114950

gcc/cp/ChangeLog:

	* module.cc (trees_out::decl_value): Stream bit indicating
	imported temploid friends early.
	(trees_in::decl_value): Use this bit with key_mergeable.
	(trees_in::key_mergeable): Allow merging attached declarations
	if they're imported temploid friends (which must be namespace
	scope).
	(module_state::read_cluster): Check for GM entities that may
	require merging even when importing from partitions.
	* name-lookup.cc (enum binding_slots): Adjust comment.
	(get_fixed_binding_slot): Always create partition slot.
	(name_lookup::search_namespace_only): Support binding vectors
	with both partition and GM entities to dedup.
	(walk_module_binding): Likewise.
	(name_lookup::adl_namespace_fns): Likewise.
	(set_module_binding): Likewise.
	(check_module_override): Use attachment of the decl when
	checking overrides rather than named_module_p.
	(lookup_imported_hidden_friend): Use partition slot for finding
	mergeable template bindings.
	* name-lookup.h (set_module_binding): Split mod_glob_flag
	parameter into separate global_p and partition_p params.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/tpl-friend-13_e.C: Adjust error message.
	* g++.dg/modules/ambig-2_a.C: New test.
	* g++.dg/modules/ambig-2_b.C: New test.
	* g++.dg/modules/part-9_a.C: New test.
	* g++.dg/modules/part-9_b.C: New test.
	* g++.dg/modules/part-9_c.C: New test.
	* g++.dg/modules/tpl-friend-15.h: New test.
	* g++.dg/modules/tpl-friend-15_a.C: New test.
	* g++.dg/modules/tpl-friend-15_b.C: New test.
	* g++.dg/modules/tpl-friend-15_c.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>

1 files changed, 33 insertions, 19 deletions

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 0f3e1d9..58ad8cb 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -2958,7 +2958,8 @@ private:
 public:
   tree decl_container ();
   tree key_mergeable (int tag, merge_kind, tree decl, tree inner, tree type,
-		      tree container, bool is_attached);
+		      tree container, bool is_attached,
+		      bool is_imported_temploid_friend);
   unsigned binfo_mergeable (tree *);
 
 private:
@@ -7806,6 +7807,7 @@ trees_out::decl_value (tree decl, depset *dep)
 		       || !TYPE_PTRMEMFUNC_P (TREE_TYPE (decl)));
 
   merge_kind mk = get_merge_kind (decl, dep);
+  bool is_imported_temploid_friend = imported_temploid_friends->get (decl);
 
   if (CHECKING_P)
     {
@@ -7841,13 +7843,11 @@ trees_out::decl_value (tree decl, depset *dep)
 		  && DECL_MODULE_ATTACH_P (not_tmpl))
 		is_attached = true;
 
-	      /* But don't consider imported temploid friends as attached,
-		 since importers will need to merge this decl even if it was
-		 attached to a different module.  */
-	      if (imported_temploid_friends->get (decl))
-		is_attached = false;
-
 	      bits.b (is_attached);
+
+	      /* Also tell the importer whether this is an imported temploid
+		 friend, which has implications for merging.  */
+	      bits.b (is_imported_temploid_friend);
 	    }
 	  bits.b (dep && dep->has_defn ());
 	}
@@ -8024,13 +8024,12 @@ trees_out::decl_value (tree decl, depset *dep)
 	}
     }
 
-  if (TREE_CODE (inner) == FUNCTION_DECL
-      || TREE_CODE (inner) == TYPE_DECL)
+  if (is_imported_temploid_friend)
     {
       /* Write imported temploid friends so that importers can reconstruct
 	 this information on stream-in.  */
       tree* slot = imported_temploid_friends->get (decl);
-      tree_node (slot ? *slot : NULL_TREE);
+      tree_node (*slot);
     }
 
   bool is_typedef = false;
@@ -8109,6 +8108,7 @@ trees_in::decl_value ()
 {
   int tag = 0;
   bool is_attached = false;
+  bool is_imported_temploid_friend = false;
   bool has_defn = false;
   unsigned mk_u = u ();
   if (mk_u >= MK_hwm || !merge_kind_name[mk_u])
@@ -8129,7 +8129,10 @@ trees_in::decl_value ()
 	{
 	  bits_in bits = stream_bits ();
 	  if (!(mk & MK_template_mask) && !state->is_header ())
-	    is_attached = bits.b ();
+	    {
+	      is_attached = bits.b ();
+	      is_imported_temploid_friend = bits.b ();
+	    }
 
 	  has_defn = bits.b ();
 	}
@@ -8234,7 +8237,7 @@ trees_in::decl_value ()
     parm_tag = fn_parms_init (inner);
 
   tree existing = key_mergeable (tag, mk, decl, inner, type, container,
-				 is_attached);
+				 is_attached, is_imported_temploid_friend);
   tree existing_inner = existing;
   if (existing)
     {
@@ -8339,8 +8342,7 @@ trees_in::decl_value ()
 	}
     }
 
-  if (TREE_CODE (inner) == FUNCTION_DECL
-      || TREE_CODE (inner) == TYPE_DECL)
+  if (is_imported_temploid_friend)
     if (tree owner = tree_node ())
       if (is_new)
 	imported_temploid_friends->put (decl, owner);
@@ -11177,7 +11179,8 @@ check_mergeable_decl (merge_kind mk, tree decl, tree ovl, merge_key const &key)
 
 tree
 trees_in::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
-			 tree type, tree container, bool is_attached)
+			 tree type, tree container, bool is_attached,
+			 bool is_imported_temploid_friend)
 {
   const char *kind = "new";
   tree existing = NULL_TREE;
@@ -11319,6 +11322,7 @@ trees_in::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
 
 	  case NAMESPACE_DECL:
 	    if (is_attached
+		&& !is_imported_temploid_friend
 		&& !(state->is_module () || state->is_partition ()))
 	      kind = "unique";
 	    else
@@ -11350,6 +11354,7 @@ trees_in::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
 	    break;
 
 	  case TYPE_DECL:
+	    gcc_checking_assert (!is_imported_temploid_friend);
 	    if (is_attached && !(state->is_module () || state->is_partition ())
 		/* Implicit member functions can come from
 		   anywhere.  */
@@ -15356,6 +15361,7 @@ module_state::read_cluster (unsigned snum)
 	    tree visible = NULL_TREE;
 	    tree type = NULL_TREE;
 	    bool dedup = false;
+	    bool global_p = false;
 
 	    /* We rely on the bindings being in the reverse order of
 	       the resulting overload set.  */
@@ -15373,6 +15379,16 @@ module_state::read_cluster (unsigned snum)
 		if (sec.get_overrun ())
 		  break;
 
+		if (!global_p)
+		  {
+		    /* Check if the decl could require GM merging.  */
+		    tree orig = get_originating_module_decl (decl);
+		    tree inner = STRIP_TEMPLATE (orig);
+		    if (!DECL_LANG_SPECIFIC (inner)
+			|| !DECL_MODULE_ATTACH_P (inner))
+		      global_p = true;
+		  }
+
 		if (decls && TREE_CODE (decl) == TYPE_DECL)
 		  {
 		    /* Stat hack.  */
@@ -15459,10 +15475,8 @@ module_state::read_cluster (unsigned snum)
 	      break; /* Bail.  */
 
 	    dump () && dump ("Binding of %P", ns, name);
-	    if (!set_module_binding (ns, name, mod,
-				     is_header () ? -1
-				     : is_module () || is_partition () ? 1
-				     : 0,
+	    if (!set_module_binding (ns, name, mod, global_p,
+				     is_module () || is_partition (),
 				     decls, type, visible))
 	      sec.set_overrun ();
 	  }