[PR c++/81574] lambda capture of function reference

https://gcc.gnu.org/ml/gcc-patches/2017-11/msg01200.html
	PR c++/81574
	* lambda.c (lambda_capture_field_type): Function references are
	always catured by reference.

	PR c++/81574
	* g++.dg/cpp1y/pr81574.C: New.

From-SVN: r254768

gcc/cp/ChangeLog

+2017-11-15  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/81574
+	* lambda.c (lambda_capture_field_type): Function references are
+	always catured by reference.
+
 2017-11-15  Martin Liska  <mliska@suse.cz>
 
 	* decl.c (begin_destructor_body): Use cp_build_fold_indirect_ref

gcc/cp/lambda.c

@@ -245,7 +245,8 @@ lambda_capture_field_type (tree expr, bool explicit_init_p,
     {
       type = non_reference (unlowered_expr_type (expr));
 
-      if (!is_this && by_reference_p)
+      if (!is_this
+	  && (by_reference_p || TREE_CODE (type) == FUNCTION_TYPE))
 	type = build_reference_type (type);
     }
 

gcc/testsuite/ChangeLog

+2017-11-15  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/81574
+	* g++.dg/cpp1y/pr81574.C: New.
+
 2017-11-15  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/82985

gcc/testsuite/g++.dg/cpp1y/pr81574.C

+// { dg-do compile { target c++14 } }
+// PR c++/81574 references to functions are captured by reference.
+
+// 8.1.5.2/10
+// For each entity captured by copy, ... an lvalue reference to the
+// referenced function type if the entity is a reference to a function
+
+void f (void (&b)())
+{
+  [=] {  b; } ();
+  [=, b(f)] { b; } ();
+  [=, b(b)] { b; } ();
+}