From 91f9108f1bd90c307daadfb4876258ec57cb746b Mon Sep 17 00:00:00 2001
From: Alexandre Oliva <aoliva@redhat.com>
Date: Fri, 23 Mar 2018 01:18:48 +0000
Subject: [PATCH] Disable auto_is_implicit_function_template_parm_p while
 parsing attributes

We don't want functions to become implicit templates just because of
random uses of auto in unexpected places.  Disabling the special
handling of auto while parsing attributes, for example, makes for
more sensible errors.


for  gcc/cp/ChangeLog

	PR c++/84610
	PR c++/84642
	PR c++/84942
	* cp-tree.h (temp_override): New template class, generalizing
	a cleanup that was only used...
	* parser.c (cp_parser_parameter_declaration_clause):
	... here for auto_is_implicit_function_template_parm_p.
	(cp_parser_gnu_attributes_opt): Use it here as well.
	(cp_parser_std_attribute): Likewise.

From-SVN: r258790
---
 gcc/cp/ChangeLog | 12 ++++++++++++
 gcc/cp/cp-tree.h | 19 +++++++++++++++++++
 gcc/cp/parser.c  | 18 ++++++++----------
 3 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index f9e7a57ec03..5dae29d23a1 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,15 @@
+2018-03-22  Alexandre Oliva <aoliva@redhat.com>
+
+	PR c++/84610
+	PR c++/84642
+	PR c++/84942
+	* cp-tree.h (temp_override): New template class, generalizing
+	a cleanup that was only used...
+	* parser.c (cp_parser_parameter_declaration_clause):
+	... here for auto_is_implicit_function_template_parm_p.
+	(cp_parser_gnu_attributes_opt): Use it here as well.
+	(cp_parser_std_attribute): Likewise.
+
 2018-03-22  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/84854
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index c07aaa5781a..c8f4bc43fa3 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1657,6 +1657,25 @@ struct warning_sentinel
   ~warning_sentinel() { flag = val; }
 };
 
+/* RAII sentinel that saves the value of a variable, optionally
+   overrides it right away, and restores its value when the sentinel
+   id destructed.  */
+
+template <typename T>
+class temp_override
+{
+  T& overridden_variable;
+  T saved_value;
+public:
+  temp_override(T& var) : overridden_variable (var), saved_value (var) {}
+  temp_override(T& var, T overrider)
+    : overridden_variable (var), saved_value (var)
+  {
+    overridden_variable = overrider;
+  }
+  ~temp_override() { overridden_variable = saved_value; }
+};
+
 /* The cached class binding level, from the most recently exited
    class, or NULL if none.  */
 
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 6dcfae125b7..34619293120 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -21196,16 +21196,8 @@ cp_parser_parameter_declaration_clause (cp_parser* parser)
   bool ellipsis_p;
   bool is_error;
 
-  struct cleanup {
-    cp_parser* parser;
-    int auto_is_implicit_function_template_parm_p;
-    ~cleanup() {
-      parser->auto_is_implicit_function_template_parm_p
-	= auto_is_implicit_function_template_parm_p;
-    }
-  } cleanup = { parser, parser->auto_is_implicit_function_template_parm_p };
-
-  (void) cleanup;
+  temp_override<bool> cleanup
+    (parser->auto_is_implicit_function_template_parm_p);
 
   if (!processing_specialization
       && !processing_template_parmlist
@@ -24968,6 +24960,9 @@ cp_parser_gnu_attributes_opt (cp_parser* parser)
 {
   tree attributes = NULL_TREE;
 
+  temp_override<bool> cleanup
+    (parser->auto_is_implicit_function_template_parm_p, false);
+
   while (true)
     {
       cp_token *token;
@@ -25159,6 +25154,9 @@ cp_parser_std_attribute (cp_parser *parser, tree attr_ns)
   tree attribute, attr_id = NULL_TREE, arguments;
   cp_token *token;
 
+  temp_override<bool> cleanup
+    (parser->auto_is_implicit_function_template_parm_p, false);
+
   /* First, parse name of the attribute, a.k.a attribute-token.  */
 
   token = cp_lexer_peek_token (parser->lexer);
-- 
2.30.2