re PR c++/80598 (-Wunused triggers for functions used in uninstantiated templates)

	PR c++/80598
	* call.c (build_over_call): In templates set TREE_USED (first_fn) when
	not calling mark_used for the benefit of -Wunused-function warning.

	* g++.dg/warn/Wunused-function4.C: New test.

From-SVN: r258370

gcc/cp/ChangeLog

+2018-03-08  Jason Merrill  <jason@redhat.com>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/80598
+	* call.c (build_over_call): In templates set TREE_USED (first_fn) when
+	not calling mark_used for the benefit of -Wunused-function warning.
+
 2018-03-06  Jason Merrill  <jason@redhat.com>
 
 	* lambda.c (is_capture_proxy_with_ref): Remove.

gcc/cp/call.c

@@ -7634,6 +7634,10 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
 
       if (undeduced_auto_decl (fn))
 	mark_used (fn, complain);
+      else
+	/* Otherwise set TREE_USED for the benefit of -Wunused-function.
+	   See PR80598.  */
+	TREE_USED (fn) = 1;
 
       return_type = TREE_TYPE (TREE_TYPE (fn));
       nargs = vec_safe_length (args);

gcc/testsuite/ChangeLog

 2018-03-08  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/80598
+	* g++.dg/warn/Wunused-function4.C: New test.
+
 	PR inline-asm/84742
 	* gcc.target/i386/pr84742-1.c: New test.
 	* gcc.target/i386/pr84742-2.c: New test.

gcc/testsuite/g++.dg/warn/Wunused-function4.C

+// PR c++/80598
+// { dg-do compile }
+// { dg-options "-Wunused-function" }
+
+static void
+foo ()		// { dg-bogus "defined but not used" }
+{
+}
+
+static void
+bar ()		// { dg-warning "defined but not used" }
+{
+}
+
+template <class T>
+int
+baz (T x)
+{
+  foo ();
+  return 0;
+}