From: Jakub Jelinek <jakub@redhat.com>
Date: Fri, 22 Jun 2018 21:27:41 +0000 (+0200)
Subject: backport: re PR c++/85952 (Bogus -Wunused-but-set-variable warning with array structu... 
X-Git-Tag: releases/gcc-7.4.0~324
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8d500ed580819f3c1a274b6a01688aef22d7b066;p=thirdparty%2Fgcc.git

backport: re PR c++/85952 (Bogus -Wunused-but-set-variable warning with array structured binding)

	Backported from mainline
	2018-05-29  Jakub Jelinek  <jakub@redhat.com>

	PR c++/85952
	* init.c (build_aggr_init): For structured binding initialized from
	array call mark_rvalue_use on the initializer.

	* g++.dg/warn/Wunused-var-33.C: New test.

From-SVN: r261965
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 9a6c7dc9adb1..e32b709acaf7 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,6 +1,12 @@
 2018-06-22  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
+	2018-05-29  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/85952
+	* init.c (build_aggr_init): For structured binding initialized from
+	array call mark_rvalue_use on the initializer.
+
 	2018-05-11  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/85696
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index e9c39ff25e6d..ec01f6b67760 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -1632,6 +1632,7 @@ build_aggr_init (tree exp, tree init, int flags, tsubst_flags_t complain)
       if (VAR_P (exp) && DECL_DECOMPOSITION_P (exp))
 	{
 	  from_array = 1;
+	  init = mark_rvalue_use (init);
 	  if (init && DECL_P (init)
 	      && !(flags & LOOKUP_ONLYCONVERTING))
 	    {
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 7669f256a446..55f2c12e8ad5 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -6,6 +6,11 @@
 	PR c++/85662
 	* g++.dg/ext/offsetof3.C: New test.
 
+	2018-05-29  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/85952
+	* g++.dg/warn/Wunused-var-33.C: New test.
+
 	2018-05-11  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/85696
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-33.C b/gcc/testsuite/g++.dg/warn/Wunused-var-33.C
new file mode 100644
index 000000000000..5f10d7810821
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-33.C
@@ -0,0 +1,37 @@
+// PR c++/85952
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wunused-but-set-variable" }
+
+int
+foo ()
+{
+  int a[2] = {1, 2};	// { dg-bogus "set but not used" } */
+  auto [x, y] = a;	// { dg-warning "decomposition declaration only available with" "" { target c++14_down } }
+  return x + y;
+}
+
+struct S { int d, e; };
+
+int
+bar ()
+{
+  S a = {1, 2};
+  auto [x, y] = a;	// { dg-warning "decomposition declaration only available with" "" { target c++14_down } }
+  return x + y;
+}
+
+int
+baz ()
+{
+  S a = {1, 2};
+  auto & [x, y] = a;	// { dg-warning "decomposition declaration only available with" "" { target c++14_down } }
+  return x + y;
+}
+
+int
+qux ()
+{
+  int a[2] = {1, 2};
+  auto & [x, y] = a;	// { dg-warning "decomposition declaration only available with" "" { target c++14_down } }
+  return x + y;
+}