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 stringstream'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 <string_view>
24#include <type_traits>
25
26#include "make_string.h"
27#include "test_allocator.h"
28#include "test_macros.h"
29
30template <class CharT>
31void test_soccc_behavior() {
32 using Alloc = SocccAllocator<CharT>;
33 using SS = std::basic_stringstream<CharT, std::char_traits<CharT>, Alloc>;
34 using S = std::basic_string<CharT, std::char_traits<CharT>, Alloc>;
35 {
36 SS ss = SS(std::ios_base::out, Alloc(10));
37
38 // [stringbuf.members]/6 specifies that the allocator is copied,
39 // not select_on_container_copy_construction'ed.
40 //
41 S copied = ss.str();
42 assert(copied.get_allocator().count_ == 10);
43 assert(ss.rdbuf()->get_allocator().count_ == 10);
44 assert(copied.empty());
45
46 // sanity-check that SOCCC does in fact work
47 assert(S(copied).get_allocator().count_ == 11);
48
49 // [stringbuf.members]/10 doesn't specify the allocator to use,
50 // but copying the allocator as-if-by moving the string makes sense.
51 //
52 S moved = std::move(ss).str();
53 assert(moved.get_allocator().count_ == 10);
54 assert(ss.rdbuf()->get_allocator().count_ == 10);
55 assert(moved.empty());
56 }
57}
58
59template <class CharT,
60 class Base = std::basic_stringbuf<CharT, std::char_traits<CharT>, std::pmr::polymorphic_allocator<CharT>>>
61struct StringBuf : Base {
62 explicit StringBuf(std::pmr::memory_resource* mr) : Base(std::ios_base::in, mr) {}
63 void public_setg(int a, int b, int c) {
64 CharT* p = this->eback();
65 assert(this->view().data() == p);
66 this->setg(p + a, p + b, p + c);
67 assert(this->eback() == p + a);
68 assert(this->view().data() == p + a);
69 }
70};
71
72template <class CharT>
73void test_allocation_is_pilfered() {
74 using SS = std::basic_stringstream<CharT, std::char_traits<CharT>, std::pmr::polymorphic_allocator<CharT>>;
75 using S = std::pmr::basic_string<CharT>;
76 alignas(void*) char buf[80 * sizeof(CharT)];
77 const CharT* initial =
78 MAKE_CSTRING(CharT, "a very long string that exceeds the small string optimization buffer length");
79 {
80 std::pmr::set_default_resource(std::pmr::null_memory_resource());
81 auto mr1 = std::pmr::monotonic_buffer_resource(buf, sizeof(buf), std::pmr::null_memory_resource());
82 SS ss = SS(S(initial, &mr1));
83 S s = std::move(ss).str();
84 assert(s == initial);
85 }
86 {
87 // Try moving-out-of a stringbuf whose view() is not the entire string.
88 // This is libc++'s behavior; libstdc++ doesn't allow such stringbufs to be created.
89 //
90 std::pmr::set_default_resource(std::pmr::null_memory_resource());
91 auto mr1 = std::pmr::monotonic_buffer_resource(buf, sizeof(buf), std::pmr::null_memory_resource());
92 auto src = StringBuf<CharT>(&mr1);
93 src.str(S(initial, &mr1));
94 src.public_setg(2, 6, 40);
95 SS ss(std::ios_base::in, &mr1);
96 *ss.rdbuf() = std::move(src);
97 LIBCPP_ASSERT(ss.view() == std::basic_string_view<CharT>(initial).substr(2, 38));
98 S s = std::move(ss).str();
99 LIBCPP_ASSERT(s == std::basic_string_view<CharT>(initial).substr(2, 38));
100 }
101}
102
103template <class CharT>
104void test_no_foreign_allocations() {
105 using SS = std::basic_stringstream<CharT, std::char_traits<CharT>, std::pmr::polymorphic_allocator<CharT>>;
106 using S = std::pmr::basic_string<CharT>;
107 const CharT* initial =
108 MAKE_CSTRING(CharT, "a very long string that exceeds the small string optimization buffer length");
109 {
110 std::pmr::set_default_resource(std::pmr::null_memory_resource());
111 auto mr1 = std::pmr::monotonic_buffer_resource(std::pmr::new_delete_resource());
112 auto ss = SS(S(initial, &mr1));
113 assert(ss.rdbuf()->get_allocator().resource() == &mr1);
114
115 // [stringbuf.members]/6 specifies that the result of `str() const &`
116 // does NOT use the default allocator; it uses the original allocator.
117 //
118 S copied = ss.str();
119 assert(copied.get_allocator().resource() == &mr1);
120 assert(ss.rdbuf()->get_allocator().resource() == &mr1);
121 assert(copied == initial);
122
123 // [stringbuf.members]/10 doesn't specify the allocator to use,
124 // but copying the allocator as-if-by moving the string makes sense.
125 //
126 S moved = std::move(ss).str();
127 assert(moved.get_allocator().resource() == &mr1);
128 assert(ss.rdbuf()->get_allocator().resource() == &mr1);
129 assert(moved == initial);
130 }
131}
132
133int main(int, char**) {
134 test_soccc_behavior<char>();
135 test_allocation_is_pilfered<char>();
136 test_no_foreign_allocations<char>();
137#ifndef TEST_HAS_NO_WIDE_CHARACTERS
138 test_soccc_behavior<wchar_t>();
139 test_allocation_is_pilfered<wchar_t>();
140 test_no_foreign_allocations<wchar_t>();
141#endif
142
143 return 0;
144}
145

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