From a98b732181472edb4591059c868082e5e708a21c Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Fri, 16 Aug 2019 20:40:36 +0000
Subject: [PATCH] re PR c++/85827 (false positive for -Wunused-but-set-variable
 because of constexpr-if)

PR c++/85827
g++.dg/cpp1z/constexpr-if29.C: New test.

From-SVN: r274587
---
 gcc/cp/ChangeLog                            |  5 ++++
 gcc/testsuite/g++.dg/cpp1z/constexpr-if29.C | 28 +++++++++++++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if29.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 938ec486d9c..c1ffe2ed94f 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2019-08-16  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/85827
+	* g++.dg/cpp1z/constexpr-if29.C: New test.
+
 2019-08-15  Jason Merrill  <jason@redhat.com>
 
 	PR c++/90393 - ICE with thow in ?:
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if29.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if29.C
new file mode 100644
index 00000000000..a40912a6fa5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if29.C
@@ -0,0 +1,28 @@
+// PR c++/85827
+// { dg-do compile { target c++17 } }
+// { dg-options "-Wunused-variable -Wunused-parameter" }
+
+template <int N> int f()
+{
+    constexpr bool _1 = N == 1;
+    constexpr bool _2 = N == 2;
+    constexpr bool _3 = N == 3;
+    
+    if constexpr (_1) {
+        return 5;
+    } else if constexpr (_2) {
+        return 1;
+    } else if constexpr (_3) {
+        return 7;
+    }
+}
+
+int a() {
+    return f<1>();
+}
+int b() {
+    return f<2>();
+}
+int c() {
+    return f<3>();
+}