2018-12-27  Joern Rennecke  <joern.rennecke@riscy-ip.com>

	* cp/parser.c: (expression_list_ref): New GTY variable.
	(cp_parser_parenthesized_expression_list): Make it reference
	expression_list.

Index: gcc/cp/parser.c
===================================================================
--- gcc/cp/parser.c	(revision 5644)
+++ gcc/cp/parser.c	(revision 5645)
@@ -7649,6 +7649,14 @@ cp_parser_postfix_dot_deref_expression (
   return postfix_expression;
 }
 
+/* When processing a member function, cgraph_node::finalize_function can
+   call ggc_collect (like if called by expand_or_defer_fn from a struct
+   member function with (function_depth <= 1)).
+   Prevent expression_list in cp_parser_parenthesized_expression_list to
+   be garbage collected then by referencing it from a GC root.  */
+typedef vec<tree, va_gc> *tree_gc_vec;
+static GTY(()) vec<tree_gc_vec, va_gc> *expression_list_ref;
+
 /* Parse a parenthesized expression-list.
 
    expression-list:
@@ -7705,6 +7713,7 @@ cp_parser_parenthesized_expression_list
     return NULL;
 
   expression_list = make_tree_vector ();
+  vec_safe_push (expression_list_ref, expression_list);
 
   /* Within a parenthesized expression, a `>' token is always
      the greater-than operator.  */
@@ -7797,6 +7806,8 @@ cp_parser_parenthesized_expression_list
 	cp_lexer_consume_token (parser->lexer);
       }
 
+  expression_list_ref->pop ();
+
   if (close_paren_loc)
     *close_paren_loc = cp_lexer_peek_token (parser->lexer)->location;