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// TODO: Change to XFAIL once https://github.com/llvm/llvm-project/issues/40340 is fixed
11// UNSUPPORTED: availability-pmr-missing
12
13// This test ensures that we properly propagate allocators from ostringstream's
14// inner string object to the new string returned from .str().
15// `str() const&` is specified to preserve the allocator (not copy the string).
16// `str() &&` isn't specified, but should preserve the allocator (move the string).
17
18#include <cassert>
19#include <memory>
20#include <memory_resource>
21#include <sstream>
22#include <string>
23#include <type_traits>
24
25#include "make_string.h"
26#include "test_allocator.h"
27#include "test_macros.h"
28
29template <class CharT>
30void test_soccc_behavior() {
31 using Alloc = SocccAllocator<CharT>;
32 using SS = std::basic_ostringstream<CharT, std::char_traits<CharT>, Alloc>;
33 using S = std::basic_string<CharT, std::char_traits<CharT>, Alloc>;
34 {
35 SS ss = SS(std::ios_base::out, Alloc(10));
36
37 // [stringbuf.members]/6 specifies that the allocator is copied,
38 // not select_on_container_copy_construction'ed.
39 //
40 S copied = ss.str();
41 assert(copied.get_allocator().count_ == 10);
42 assert(ss.rdbuf()->get_allocator().count_ == 10);
43 assert(copied.empty());
44
45 // sanity-check that SOCCC does in fact work
46 assert(S(copied).get_allocator().count_ == 11);
47
48 // [stringbuf.members]/10 doesn't specify the allocator to use,
49 // but copying the allocator as-if-by moving the string makes sense.
50 //
51 S moved = std::move(ss).str();
52 assert(moved.get_allocator().count_ == 10);
53 assert(ss.rdbuf()->get_allocator().count_ == 10);
54 assert(moved.empty());
55 }
56}
57
58template <class CharT>
59void test_allocation_is_pilfered() {
60 using SS = std::basic_ostringstream<CharT, std::char_traits<CharT>, std::pmr::polymorphic_allocator<CharT>>;
61 using S = std::pmr::basic_string<CharT>;
62 alignas(void*) char buf[80 * sizeof(CharT)];
63 const CharT* initial =
64 MAKE_CSTRING(CharT, "a very long string that exceeds the small string optimization buffer length");
65 {
66 std::pmr::set_default_resource(std::pmr::null_memory_resource());
67 auto mr1 = std::pmr::monotonic_buffer_resource(buf, sizeof(buf), std::pmr::null_memory_resource());
68 SS ss = SS(S(initial, &mr1));
69 S s = std::move(ss).str();
70 assert(s == initial);
71 }
72}
73
74template <class CharT>
75void test_no_foreign_allocations() {
76 using SS = std::basic_ostringstream<CharT, std::char_traits<CharT>, std::pmr::polymorphic_allocator<CharT>>;
77 using S = std::pmr::basic_string<CharT>;
78 const CharT* initial =
79 MAKE_CSTRING(CharT, "a very long string that exceeds the small string optimization buffer length");
80 {
81 std::pmr::set_default_resource(std::pmr::null_memory_resource());
82 auto mr1 = std::pmr::monotonic_buffer_resource(std::pmr::new_delete_resource());
83 auto ss = SS(S(initial, &mr1));
84 assert(ss.rdbuf()->get_allocator().resource() == &mr1);
85
86 // [stringbuf.members]/6 specifies that the result of `str() const &`
87 // does NOT use the default allocator; it uses the original allocator.
88 //
89 S copied = ss.str();
90 assert(copied.get_allocator().resource() == &mr1);
91 assert(ss.rdbuf()->get_allocator().resource() == &mr1);
92 assert(copied == initial);
93
94 // [stringbuf.members]/10 doesn't specify the allocator to use,
95 // but copying the allocator as-if-by moving the string makes sense.
96 //
97 S moved = std::move(ss).str();
98 assert(moved.get_allocator().resource() == &mr1);
99 assert(ss.rdbuf()->get_allocator().resource() == &mr1);
100 assert(moved == initial);
101 }
102}
103
104int main(int, char**) {
105 test_soccc_behavior<char>();
106 test_allocation_is_pilfered<char>();
107 test_no_foreign_allocations<char>();
108#ifndef TEST_HAS_NO_WIDE_CHARACTERS
109 test_soccc_behavior<wchar_t>();
110 test_allocation_is_pilfered<wchar_t>();
111 test_no_foreign_allocations<wchar_t>();
112#endif
113
114 return 0;
115}
116

source code of libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.members/str.allocator_propagation.pass.cpp