c++: local externs in templates do not get template head

Now we consistently mark local externs with DECL_LOCAL_DECL_P, we can
teach the template machinery not to give them a TEMPLATE_DECL head,
and the instantiation machinery treat them as the local specialiations
they are.  (openmp UDRs also fall into this category, and are dealt
with similarly.)

	gcc/cp/
	* pt.c (push_template_decl_real): Don't attach a template head to
	local externs.
	(tsubst_function_decl): Add support for headless local extern
	decls.
	(tsubst_decl): Add support for headless local extern decls.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 0f52a9ed77dbc71c7fd884ad5985d879bb09094c..8124efcbe243466e71b17d2f3ce5ae18b54b50cb 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -6071,7 +6071,11 @@ push_template_decl_real (tree decl, bool is_friend)
     {
       if (is_primary)
        retrofit_lang_decl (decl);
-      if (DECL_LANG_SPECIFIC (decl))
+      if (DECL_LANG_SPECIFIC (decl)
+         && ((TREE_CODE (decl) != VAR_DECL
+              && TREE_CODE (decl) != FUNCTION_DECL)
+             || !ctx
+             || !DECL_LOCAL_DECL_P (decl)))
        DECL_TEMPLATE_INFO (decl) = info;
     }
 
@@ -13701,14 +13705,20 @@ static tree
 tsubst_function_decl (tree t, tree args, tsubst_flags_t complain,
                      tree lambda_fntype)
 {
-  tree gen_tmpl, argvec;
+  tree gen_tmpl = NULL_TREE, argvec = NULL_TREE;
   hashval_t hash = 0;
   tree in_decl = t;
 
   /* Nobody should be tsubst'ing into non-template functions.  */
-  gcc_assert (DECL_TEMPLATE_INFO (t) != NULL_TREE);
+  gcc_assert (DECL_TEMPLATE_INFO (t) != NULL_TREE
+             || DECL_LOCAL_DECL_P (t));
 
-  if (TREE_CODE (DECL_TI_TEMPLATE (t)) == TEMPLATE_DECL)
+  if (DECL_LOCAL_DECL_P (t))
+    {
+      if (tree spec = retrieve_local_specialization (t))
+       return spec;
+    }
+  else if (TREE_CODE (DECL_TI_TEMPLATE (t)) == TEMPLATE_DECL)
     {
       /* If T is not dependent, just return it.  */
       if (!uses_template_parms (DECL_TI_ARGS (t))
@@ -13958,6 +13968,11 @@ tsubst_function_decl (tree t, tree args, tsubst_flags_t complain,
          && !uses_template_parms (argvec))
        tsubst_default_arguments (r, complain);
     }
+  else if (DECL_LOCAL_DECL_P (r))
+    {
+      if (!cp_unevaluated_operand)
+       register_local_specialization (r, t);
+    }
   else
     DECL_TEMPLATE_INFO (r) = NULL_TREE;
 
@@ -14503,11 +14518,8 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
       {
        tree argvec = NULL_TREE;
        tree gen_tmpl = NULL_TREE;
-       tree spec;
        tree tmpl = NULL_TREE;
-       tree ctx;
        tree type = NULL_TREE;
-       bool local_p;
 
        if (TREE_TYPE (t) == error_mark_node)
          RETURN (error_mark_node);
@@ -14529,19 +14541,13 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
 
        /* Check to see if we already have the specialization we
           need.  */
-       spec = NULL_TREE;
-       if (DECL_CLASS_SCOPE_P (t) || DECL_NAMESPACE_SCOPE_P (t))
+       tree spec = NULL_TREE;
+       bool local_p = false;
+       tree ctx = DECL_CONTEXT (t);
+       if (!(VAR_P (t) && DECL_LOCAL_DECL_P (t))
+           && (DECL_CLASS_SCOPE_P (t) || DECL_NAMESPACE_SCOPE_P (t)))
          {
-           /* T is a static data member or namespace-scope entity.
-              We have to substitute into namespace-scope variables
-              (not just variable templates) because of cases like:
-
-                template <class T> void f() { extern T t; }
-
-              where the entity referenced is not known until
-              instantiation time.  */
            local_p = false;
-           ctx = DECL_CONTEXT (t);
            if (DECL_CLASS_SCOPE_P (t))
              {
                ctx = tsubst_aggr_type (ctx, args,
@@ -14581,10 +14587,11 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
          }
        else
          {
+           if (!(VAR_P (t) && DECL_LOCAL_DECL_P (t)))
+             /* Subsequent calls to pushdecl will fill this in.  */
+             ctx = NULL_TREE;
            /* A local variable.  */
            local_p = true;
-           /* Subsequent calls to pushdecl will fill this in.  */
-           ctx = NULL_TREE;
            /* Unless this is a reference to a static variable from an
               enclosing function, in which case we need to fill it in now.  */
            if (TREE_STATIC (t))