Fix libc++ bug #20039: 'Constructing std::function from empty compatible std::function results in half-empty state' Thanks to Agustin Berge for the report, and for his and Eric Fiselier's work on a fix.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@212070 91177308-0d34-0410-b5e6-96231b3b80d8

test/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/copy.pass.cpp

@@ -99,6 +99,18 @@ int main()
     assert(f2.target<int(*)(int)>() == 0);
     assert(f2.target<A>() == 0);
     }
+    {
+    std::function<int(int)> f;
+    assert(new_called == 0);
+    assert(f.target<int(*)(int)>() == 0);
+    assert(f.target<A>() == 0);
+    assert(!f);
+    std::function<long(int)> g = f;
+    assert(new_called == 0);
+    assert(g.target<long(*)(int)>() == 0);
+    assert(g.target<A>() == 0);
+    assert(!g);
+    }
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     assert(new_called == 0);
     {

test/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/no-variadics.pass.cpp

@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <functional>
+
+// class function<R()>
+
+// template<class F> function(F);
+
+#define _LIBCPP_HAS_NO_VARIADICS
+#include <functional>
+#include <cassert>
+
+int main()
+{
+    std::function<void()> f(static_cast<void(*)()>(0));
+    assert(!f);
+}