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
11// If we have a copy-propagating cache, when we copy ZeroOnDestroy, we will get a
12// dangling reference to the copied-from object. This test ensures that we do not
13// propagate the cache on copy.
14
15#include <ranges>
16
17#include <cstddef>
18#include <cstring>
19
20#include "test_macros.h"
21#include "types.h"
22
23struct ZeroOnDestroy : std::ranges::view_base {
24 unsigned count = 0;
25 int buff[8] = {1, 2, 3, 4, 5, 6, 7, 8};
26
27 constexpr ForwardIter begin() { return ForwardIter(buff); }
28 constexpr ForwardIter begin() const { return ForwardIter(); }
29 constexpr ForwardIter end() { return ForwardIter(buff + 8); }
30 constexpr ForwardIter end() const { return ForwardIter(); }
31
32 ZeroOnDestroy() = default;
33 ZeroOnDestroy(const ZeroOnDestroy&) = default;
34 ZeroOnDestroy& operator=(const ZeroOnDestroy&) = default;
35 ~ZeroOnDestroy() {
36 std::memset(s: buff, c: 0, n: 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
50int main(int, char**) {
51 auto noDanglingCache = 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(*noDanglingCache.begin() == 5);
55
56 return 0;
57}
58

source code of libcxx/test/std/ranges/range.adaptors/range.drop/dangling.cache.pass.cpp