1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 // UNSUPPORTED: c++03, c++11, c++14, c++17
10 // UNSUPPORTED: libcpp-no-concepts
11 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
12 
13 // If we have a copy-propagating cache, when we copy ZeroOnDestroy, we will get a
14 // dangling reference to the copied-from object. This test ensures that we do not
15 // propagate the cache on copy.
16 
17 #include <ranges>
18 
19 #include <cstddef>
20 #include <cstring>
21 
22 #include "test_macros.h"
23 #include "types.h"
24 
25 struct ZeroOnDestroy : std::ranges::view_base {
26   unsigned count = 0;
27   int buff[8] = {1, 2, 3, 4, 5, 6, 7, 8};
28 
29   constexpr ForwardIter begin() { return ForwardIter(buff); }
30   constexpr ForwardIter begin() const { return ForwardIter(); }
31   constexpr ForwardIter end() { return ForwardIter(buff + 8); }
32   constexpr ForwardIter end() const { return ForwardIter(); }
33 
34   ~ZeroOnDestroy() {
35     std::memset(buff, 0, sizeof(buff));
36   }
37 
38   static auto dropFirstFour() {
39     ZeroOnDestroy zod;
40     std::ranges::drop_view dv(zod, 4);
41     // Make sure we call begin here so the next call to begin will
42     // use the cached iterator.
43     assert(*dv.begin() == 5);
44     // Intentionally invoke the copy ctor here.
45     return std::ranges::drop_view(dv);
46   }
47 };
48 
49 int main(int, char**) {
50   auto noDanlingCache = ZeroOnDestroy::dropFirstFour();
51   // If we use the cached version, it will reference the copied-from view.
52   // Worst case this is a segfault, best case it's an assertion fired.
53   assert(*noDanlingCache.begin() == 5);
54 
55   return 0;
56 }
57