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