From bc61048a143b10d8efdc50195f2fc949d036ca92 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Sat, 11 Feb 2017 12:29:45 -0500
Subject: [PATCH] PR c++/77790 - ICE with auto function in C++11 mode

	* decl.c (undeduced_auto_decl): Remove C++14 limitation.
	(require_deduced_type): Add complain parm, return bool.
	* cp-tree.h: Adjust.
	* decl2.c (mark_used): Use require_deduced_type.

From-SVN: r245358
---
 gcc/cp/ChangeLog                       |  8 ++++++++
 gcc/cp/cp-tree.h                       |  2 +-
 gcc/cp/decl.c                          | 15 ++++++++++-----
 gcc/cp/decl2.c                         | 17 +++++------------
 gcc/testsuite/g++.dg/cpp0x/auto41.C    |  2 +-
 gcc/testsuite/g++.dg/cpp1y/auto-fn35.C | 11 +++++++++++
 6 files changed, 36 insertions(+), 19 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/auto-fn35.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 4523d128ccc..553db8a126b 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,11 @@
+2017-02-11  Jason Merrill  <jason@redhat.com>
+
+	PR c++/77790 - ICE with auto function in C++11 mode
+	* decl.c (undeduced_auto_decl): Remove C++14 limitation.
+	(require_deduced_type): Add complain parm, return bool.
+	* cp-tree.h: Adjust.
+	* decl2.c (mark_used): Use require_deduced_type.
+
 2017-02-10  Jason Merrill  <jason@redhat.com>
 
 	PR c++/78908 - template ops and bitfields
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index a4109261d48..0146332181c 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -5909,7 +5909,7 @@ extern tree reshape_init                        (tree, tree, tsubst_flags_t);
 extern tree next_initializable_field (tree);
 extern tree fndecl_declared_return_type		(tree);
 extern bool undeduced_auto_decl			(tree);
-extern void require_deduced_type		(tree);
+extern bool require_deduced_type		(tree, tsubst_flags_t = tf_warning_or_error);
 
 extern tree finish_case_label			(location_t, tree, tree);
 extern tree cxx_maybe_build_cleanup		(tree, tsubst_flags_t);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 734a6c751d0..2292a3a2ac9 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -16138,24 +16138,29 @@ fndecl_declared_return_type (tree fn)
   return TREE_TYPE (TREE_TYPE (fn));
 }
 
-/* Returns true iff DECL was declared with an auto return type and it has
+/* Returns true iff DECL was declared with an auto type and it has
    not yet been deduced to a real type.  */
 
 bool
 undeduced_auto_decl (tree decl)
 {
-  if (cxx_dialect < cxx14)
+  if (cxx_dialect < cxx11)
     return false;
   return type_uses_auto (TREE_TYPE (decl));
 }
 
 /* Complain if DECL has an undeduced return type.  */
 
-void
-require_deduced_type (tree decl)
+bool
+require_deduced_type (tree decl, tsubst_flags_t complain)
 {
   if (undeduced_auto_decl (decl))
-    error ("use of %qD before deduction of %<auto%>", decl);
+    {
+      if (complain & tf_error)
+	error ("use of %qD before deduction of %<auto%>", decl);
+      return false;
+    }
+  return true;
 }
 
 #include "gt-cp-decl.h"
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index cecb6a145b7..efc0b0e6974 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -5084,12 +5084,9 @@ mark_used (tree decl, tsubst_flags_t complain)
       || DECL_LANG_SPECIFIC (decl) == NULL
       || DECL_THUNK_P (decl))
     {
-      if (!processing_template_decl && type_uses_auto (TREE_TYPE (decl)))
-	{
-	  if (complain & tf_error)
-	    error ("use of %qD before deduction of %<auto%>", decl);
-	  return false;
-	}
+      if (!processing_template_decl
+	  && !require_deduced_type (decl, complain))
+	return false;
       return true;
     }
 
@@ -5117,12 +5114,8 @@ mark_used (tree decl, tsubst_flags_t complain)
       && uses_template_parms (DECL_TI_ARGS (decl)))
     return true;
 
-  if (undeduced_auto_decl (decl))
-    {
-      if (complain & tf_error)
-	error ("use of %qD before deduction of %<auto%>", decl);
-      return false;
-    }
+  if (!require_deduced_type (decl, complain))
+    return false;
 
   /* If we don't need a value, then we don't need to synthesize DECL.  */
   if (cp_unevaluated_operand || in_discarded_stmt)
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto41.C b/gcc/testsuite/g++.dg/cpp0x/auto41.C
index b1551e2e580..a1065af0741 100644
--- a/gcc/testsuite/g++.dg/cpp0x/auto41.C
+++ b/gcc/testsuite/g++.dg/cpp0x/auto41.C
@@ -2,4 +2,4 @@
 // { dg-do compile { target c++11 } }
 
 auto foo();			// { dg-error "auto" "" { target { ! c++14 } } }
-auto fp = foo;			// { dg-error "auto" "" { target c++14 } }
+auto fp = foo;			// { dg-error "auto" }
diff --git a/gcc/testsuite/g++.dg/cpp1y/auto-fn35.C b/gcc/testsuite/g++.dg/cpp1y/auto-fn35.C
new file mode 100644
index 00000000000..a40817442d7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/auto-fn35.C
@@ -0,0 +1,11 @@
+// PR c++/77790
+// { dg-do compile { target c++11 } }
+
+template < typename S > struct A
+{
+  // { dg-error "" "" { target c++11_only } .+1 }
+  template < typename T > static auto f () { return 0; } 
+  template < class U = decltype (f < S > ()) > int g () { return 0; }
+};
+
+auto a = A < int > {}.g ();