From af7128621e54f04b90589bb0c3e1ef271c239265 Mon Sep 17 00:00:00 2001
From: Martin Sebor <msebor@redhat.com>
Date: Tue, 13 Apr 2021 14:53:26 -0600
Subject: [PATCH] PR tree-optimization/82800 - Incorrect warning on "may be
 used uninitialized in variadic template code

gcc/testsuite/ChangeLog:
	PR tree-optimization/82800
	* g++.dg/warn/uninit-pr82800.C: New test.
---
 gcc/testsuite/g++.dg/warn/uninit-pr82800.C | 43 ++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/warn/uninit-pr82800.C

diff --git a/gcc/testsuite/g++.dg/warn/uninit-pr82800.C b/gcc/testsuite/g++.dg/warn/uninit-pr82800.C
new file mode 100644
index 000000000000..dc3ce5d89e31
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/uninit-pr82800.C
@@ -0,0 +1,43 @@
+/* PR 82800 - Incorrect warning on "may be used uninitialized in
+   variadic template code
+   { dg-do compile { target c++11 } }
+   { dg-options "-O2 -Wall" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+extern "C" int rand ();
+
+struct Maker
+{
+  double makeConst()
+  {
+    return pick<double>(0, 0, 0, 0, 0, 0, 1);   // { dg-bogus "uninitialized" }
+  }
+
+  template<typename T, typename... Args>
+  T pick(T first, Args... args)
+  {
+    return pickGivenNum<T>(rand(), first, args...);
+  }
+
+  template<typename T>
+  T pickGivenNum(size_t num, T first)
+  {
+    if (num != 0) __builtin_abort();
+    return first;
+  }
+
+  template<typename T, typename... Args>
+  T pickGivenNum(size_t num, T first, Args... args)
+  {
+    if (num == 0) return first;
+    return pickGivenNum<T>(num - 1, args...);
+  }
+};
+
+int main ()
+{
+  Maker maker;
+  maker.makeConst();
+  maker.makeConst();
+}