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: gcc-10
12 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
13 
14 // If we have a copy-propagating cache, when we copy ZeroOnDestroy, we will get a
15 // dangling reference to the copied-from object. This test ensures that we do not
16 // propagate the cache on copy.
17 
18 #include <ranges>
19 
20 #include <cstddef>
21 #include <cstring>
22 
23 #include "test_macros.h"
24 #include "types.h"
25 
26 struct ZeroOnDestroy : std::ranges::view_base {
27   unsigned count = 0;
28   int buff[8] = {1, 2, 3, 4, 5, 6, 7, 8};
29 
30   constexpr ForwardIter begin() { return ForwardIter(buff); }
31   constexpr ForwardIter begin() const { return ForwardIter(); }
32   constexpr ForwardIter end() { return ForwardIter(buff + 8); }
33   constexpr ForwardIter end() const { return ForwardIter(); }
34 
35   ~ZeroOnDestroy() {
36     memset(buff, 0, sizeof(buff));
37   }
38 
39   static auto dropFirstFour() {
40     ZeroOnDestroy zod;
41     std::ranges::drop_view dv(zod, 4);
42     // Make sure we call begin here so the next call to begin will
43     // use the cached iterator.
44     assert(*dv.begin() == 5);
45     // Intentionally invoke the copy ctor here.
46     return std::ranges::drop_view(dv);
47   }
48 };
49 
50 int main(int, char**) {
51   auto noDanlingCache = ZeroOnDestroy::dropFirstFour();
52   // If we use the cached version, it will reference the copied-from view.
53   // Worst case this is a segfault, best case it's an assertion fired.
54   assert(*noDanlingCache.begin() == 5);
55 
56   return 0;
57 }
58