Re: [C++ Patch/RFC] PR 71169 ("[7/8 Regression] ICE on invalid C++ code in pop_nested_class"), PR 71832 and more

[Paolo Carlini <paolo dot carlini at oracle dot com>]

Hi again,

On 07/03/2018 21:49, Paolo Carlini wrote:
> ... If you ask my opinion, at the moment I still believe that the best 
> solution would be doing something at parsing time, save the 
> information, in a more elegant way, maybe adding a special "erroneous 
> TREE_VEC" flag to the TREE_VECs. I don't know exactly. Even better a 
> unique flag for all the template parameter lists of each class.
Just to explain more *concretely* what I had in mind, I quickly hacked 
the below, which would be a *minimal* implementation of my idea. It 
should be also possible to consolidate the flags of the various 
TMPL_ARGS_LEVELs to the flag of the TREE_VEC returned by TI_ARGS 
(get_template_info). That would be fantastic: ideally I would like to 
see an O(0) any_erroneous_template_args_p. Maybe we can do that when we 
use SET_TMPL_ARGS_LEVEL? Probably it would take you 5 mins to implement 
all of that. Or, I was thinking, something completely different, instead 
of fiddling with TREE_VECs, have something in DECL_TEMPLATE_INFO? (see 
again my remark about the 5 mins ;)

Paolo.

//////////////////

Index: cp-tree.h
===================================================================
--- cp-tree.h	(revision 258355)
+++ cp-tree.h	(working copy)
@@ -592,6 +592,8 @@ struct GTY(()) ptrmem_cst {
 };
 typedef struct ptrmem_cst * ptrmem_cst_t;
 
+#define ERRONEOUS_TREE_VEC(NODE) ((NODE)->base.u.bits.lang_flag_0)
+
 #define CLEANUP_P(NODE)		TREE_LANG_FLAG_0 (TRY_BLOCK_CHECK (NODE))
 
 #define BIND_EXPR_TRY_BLOCK(NODE) \
@@ -6558,6 +6560,7 @@ extern int processing_template_parmlist;
 extern bool dependent_type_p			(tree);
 extern bool dependent_scope_p			(tree);
 extern bool any_dependent_template_arguments_p  (const_tree);
+extern bool any_erroneous_template_args_p	(const_tree);
 extern bool dependent_template_p		(tree);
 extern bool dependent_template_id_p		(tree, tree);
 extern bool type_dependent_expression_p		(tree);
Index: parser.c
===================================================================
--- parser.c	(revision 258355)
+++ parser.c	(working copy)
@@ -22682,6 +22682,8 @@ cp_parser_class_specifier_1 (cp_parser* parser)
       FOR_EACH_VEC_SAFE_ELT (unparsed_funs_with_default_args, ix, e)
 	{
 	  decl = e->decl;
+	  if (any_erroneous_template_args_p (decl))
+	    continue;
 	  /* If there are default arguments that have not yet been processed,
 	     take care of them now.  */
 	  if (class_type != e->class_type)
@@ -22704,6 +22706,8 @@ cp_parser_class_specifier_1 (cp_parser* parser)
       save_ccr = current_class_ref;
       FOR_EACH_VEC_SAFE_ELT (unparsed_nsdmis, ix, decl)
 	{
+	  if (any_erroneous_template_args_p (decl))
+	    continue;
 	  if (class_type != DECL_CONTEXT (decl))
 	    {
 	      if (pushed_scope)
@@ -27642,6 +27646,9 @@ cp_parser_late_parsing_for_member (cp_parser* pars
   if (DECL_FUNCTION_TEMPLATE_P (member_function))
     member_function = DECL_TEMPLATE_RESULT (member_function);
 
+  if (any_erroneous_template_args_p (member_function))
+    return;
+
   /* There should not be any class definitions in progress at this
      point; the bodies of members are only parsed outside of all class
      definitions.  */
Index: pt.c
===================================================================
--- pt.c	(revision 258355)
+++ pt.c	(working copy)
@@ -4459,6 +4459,8 @@ end_template_parm_list (tree parms)
     {
       next = TREE_CHAIN (parm);
       TREE_VEC_ELT (saved_parmlist, nparms) = parm;
+      if (error_operand_p (parm))
+	ERRONEOUS_TREE_VEC (saved_parmlist) = true;
       TREE_CHAIN (parm) = NULL_TREE;
     }
 
@@ -25048,6 +25050,42 @@ any_dependent_template_arguments_p (const_tree arg
   return false;
 }
 
+/* Returns true if ARGS contains any errors.  */
+
+bool
+any_erroneous_template_args_p (const_tree args)
+{
+  int i;
+  int j;
+
+  if (args && TREE_CODE (args) != TREE_VEC)
+    {
+      if (tree ti = get_template_info (args))
+	args = TI_ARGS (ti);
+      else
+	args = NULL_TREE;
+    }
+
+  if (!args)
+    return false;
+  if (args == error_mark_node)
+    return true;
+
+  for (i = 0; i < TMPL_ARGS_DEPTH (args); ++i)
+    {
+      const_tree level = TMPL_ARGS_LEVEL (args, i + 1);
+      if (ERRONEOUS_TREE_VEC (level))
+	return true;
+      /*
+      for (j = 0; j < TREE_VEC_LENGTH (level); ++j)
+	if (error_operand_p (TREE_VEC_ELT (level, j)))
+	  return true;
+      */
+    }
+
+  return false;
+}
+
 /* Returns TRUE if the template TMPL is type-dependent.  */
 
 bool