1 //
2 // Tests for
3 //  bounded_ptr& operator+=(std::ptrdiff_t n);
4 //
5 
6 #include <libkern/c++/bounded_ptr.h>
7 #include <array>
8 #include <cstddef>
9 #include <cstdint>
10 #include <limits>
11 #include <darwintest.h>
12 #include <darwintest_utils.h>
13 #include "test_utils.h"
14 
15 #define _assert(...) T_ASSERT_TRUE((__VA_ARGS__), # __VA_ARGS__)
16 
17 struct T { int i; };
18 
19 namespace {
20 struct tracking_policy {
21 	static bool did_trap;
22 	static void
23 	trap(char const*)
24 	{
25 		did_trap = true;
26 	}
27 };
28 bool tracking_policy::did_trap = false;
29 }
30 
31 template <typename T, typename QualT>
32 static void
33 tests()
34 {
35 	std::array<T, 5> array = {T{0}, T{1}, T{2}, T{3}, T{4}};
36 
37 	// Add-assign positive offsets
38 	// T{0}     T{1}     T{2}     T{3}     T{4}     <one-past-last>
39 	//   ^                                                ^
40 	//   |                                                |
41 	// begin,ptr                                         end
42 	{
43 		test_bounded_ptr<QualT> ptr(array.begin(), array.begin(), array.end());
44 		auto& ref = ptr += 0;
45 		_assert(&ref == &ptr);
46 		_assert(&*ptr == &array[0]);
47 	}
48 	{
49 		test_bounded_ptr<QualT> ptr(array.begin(), array.begin(), array.end());
50 		auto& ref = ptr += 1;
51 		_assert(&ref == &ptr);
52 		_assert(&*ptr == &array[1]);
53 	}
54 	{
55 		test_bounded_ptr<QualT> ptr(array.begin(), array.begin(), array.end());
56 		auto& ref = ptr += 2;
57 		_assert(&ref == &ptr);
58 		_assert(&*ptr == &array[2]);
59 	}
60 	{
61 		test_bounded_ptr<QualT> ptr(array.begin(), array.begin(), array.end());
62 		auto& ref = ptr += 3;
63 		_assert(&ref == &ptr);
64 		_assert(&*ptr == &array[3]);
65 	}
66 	{
67 		test_bounded_ptr<QualT> ptr(array.begin(), array.begin(), array.end());
68 		auto& ref = ptr += 4;
69 		_assert(&ref == &ptr);
70 		_assert(&*ptr == &array[4]);
71 	}
72 	{
73 		test_bounded_ptr<QualT> ptr(array.begin(), array.begin(), array.end());
74 		auto& ref = ptr += 5;
75 		_assert(&ref == &ptr);
76 		_assert(ptr == array.end());
77 	}
78 
79 	// Add-assign negative offsets
80 	// T{0}     T{1}     T{2}     T{3}     T{4}     <one-past-last>
81 	//   ^                                                ^
82 	//   |                                                |
83 	// begin                                           end,ptr
84 	{
85 		test_bounded_ptr<QualT> ptr(array.end(), array.begin(), array.end());
86 		auto& ref = ptr += 0;
87 		_assert(&ref == &ptr);
88 		_assert(ptr == array.end());
89 	}
90 	{
91 		test_bounded_ptr<QualT> ptr(array.end(), array.begin(), array.end());
92 		auto& ref = ptr += -1;
93 		_assert(&ref == &ptr);
94 		_assert(&*ptr == &array[4]);
95 	}
96 	{
97 		test_bounded_ptr<QualT> ptr(array.end(), array.begin(), array.end());
98 		auto& ref = ptr += -2;
99 		_assert(&ref == &ptr);
100 		_assert(&*ptr == &array[3]);
101 	}
102 	{
103 		test_bounded_ptr<QualT> ptr(array.end(), array.begin(), array.end());
104 		auto& ref = ptr += -3;
105 		_assert(&ref == &ptr);
106 		_assert(&*ptr == &array[2]);
107 	}
108 	{
109 		test_bounded_ptr<QualT> ptr(array.end(), array.begin(), array.end());
110 		auto& ref = ptr += -4;
111 		_assert(&ref == &ptr);
112 		_assert(&*ptr == &array[1]);
113 	}
114 	{
115 		test_bounded_ptr<QualT> ptr(array.end(), array.begin(), array.end());
116 		auto& ref = ptr += -5;
117 		_assert(&ref == &ptr);
118 		_assert(&*ptr == &array[0]);
119 	}
120 
121 	// Make sure we trap on arithmetic overflow in the number of bytes calculation
122 	{
123 		std::ptrdiff_t sizeof_T = sizeof(T); // avoid promotion to unsigned in calculations
124 
125 		// largest (most positive) n for the number of bytes `n * sizeof(T)` not to overflow ptrdiff_t
126 		std::ptrdiff_t max_n = std::numeric_limits<std::ptrdiff_t>::max() / sizeof_T;
127 
128 		// smallest (most negative) n for the number of bytes `n * sizeof(T)` not to overflow ptrdiff_t
129 		std::ptrdiff_t min_n = std::numeric_limits<std::ptrdiff_t>::min() / sizeof_T;
130 
131 		// Overflow with a positive offset
132 		{
133 			libkern::bounded_ptr<QualT, tracking_policy> ptr(array.begin(), array.begin(), array.end());
134 			tracking_policy::did_trap = false;
135 			ptr += max_n + 1;
136 			_assert(tracking_policy::did_trap);
137 		}
138 
139 		// Overflow with a negative offset
140 		{
141 			libkern::bounded_ptr<QualT, tracking_policy> ptr(array.begin(), array.begin(), array.end());
142 			tracking_policy::did_trap = false;
143 			ptr += min_n - 1;
144 			_assert(tracking_policy::did_trap);
145 		}
146 	}
147 
148 	// Make sure we trap on arithmetic overflow in the offset calculation
149 	//
150 	// To avoid running into the overflow of `n * sizeof(T)` when ptrdiff_t
151 	// is the same size as int32_t, we test the offset overflow check by
152 	// successive addition of smaller offsets.
153 	//
154 	// We basically push the offset right to its limit, and then push it
155 	// past its limit to watch it overflow.
156 	{
157 		std::int64_t sizeof_T = sizeof(T); // avoid promotion to unsigned in calculations
158 
159 		// largest (most positive) n for the number of bytes `n * sizeof(T)` not to overflow the int32_t offset
160 		std::int64_t max_n = std::numeric_limits<std::int32_t>::max() / sizeof_T;
161 
162 		// smallest (most negative) n for the number of bytes `n * sizeof(T)` not to overflow the int32_t offset
163 		std::int64_t min_n = std::numeric_limits<std::int32_t>::min() / sizeof_T;
164 
165 		// Add positive offsets
166 		{
167 			libkern::bounded_ptr<QualT, tracking_policy> ptr(array.begin(), array.begin(), array.end());
168 			tracking_policy::did_trap = false;
169 			ptr += static_cast<ptrdiff_t>(max_n / 2);
170 			_assert(!tracking_policy::did_trap);
171 			ptr += static_cast<ptrdiff_t>(max_n / 2);
172 			_assert(!tracking_policy::did_trap);
173 			ptr += (max_n % 2);
174 			_assert(!tracking_policy::did_trap); // offset is now right at its positive limit
175 			ptr += 1;
176 			_assert(tracking_policy::did_trap);
177 		}
178 
179 		// Add negative offsets
180 		{
181 			libkern::bounded_ptr<QualT, tracking_policy> ptr(array.begin(), array.begin(), array.end());
182 			tracking_policy::did_trap = false;
183 			ptr += static_cast<ptrdiff_t>(min_n / 2);
184 			_assert(!tracking_policy::did_trap);
185 			ptr += static_cast<ptrdiff_t>(min_n / 2);
186 			_assert(!tracking_policy::did_trap);
187 			ptr += (min_n % 2);
188 			_assert(!tracking_policy::did_trap); // offset is now right at its negative limit
189 			ptr += -1;
190 			_assert(tracking_policy::did_trap);
191 		}
192 	}
193 }
194 
195 T_DECL(arith_add_assign, "bounded_ptr.arith.add_assign") {
196 	tests<T, T>();
197 	tests<T, T const>();
198 	tests<T, T volatile>();
199 	tests<T, T const volatile>();
200 }
201