Keir Mierle | 32829d3 | 2020-11-25 15:38:40 -0800 | [diff] [blame] | 1 | // Copyright 2020 The Pigweed Authors |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| 4 | // use this file except in compliance with the License. You may obtain a copy of |
| 5 | // the License at |
| 6 | // |
| 7 | // https://www.apache.org/licenses/LICENSE-2.0 |
| 8 | // |
| 9 | // Unless required by applicable law or agreed to in writing, software |
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| 11 | // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| 12 | // License for the specific language governing permissions and limitations under |
| 13 | // the License. |
| 14 | // |
| 15 | // This tests the system installed C standard library version of memset. |
| 16 | // |
| 17 | // Note: We have caught real production bugs with these tests. Do not assume |
| 18 | // your vendor's C library is correct! For standard C functions like memset and |
| 19 | // memcpy, there are compiler intrisics which assume that the C standard is |
| 20 | // followed. If the implemention of memset or memcpy does not exactly follow |
| 21 | // the standard, subtle and hard to track down bugs can be the result. |
| 22 | |
| 23 | #include <array> |
| 24 | #include <cstring> |
| 25 | #include <numeric> |
| 26 | |
| 27 | #include "gtest/gtest.h" |
| 28 | |
| 29 | namespace pw { |
| 30 | namespace { |
| 31 | |
| 32 | // From the ISO C standard: |
| 33 | // http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf |
| 34 | // |
| 35 | // Section 7.21.6.1: memset(void *s, int c, size_t n) |
| 36 | // |
| 37 | // void* memset(void* buffer, |
| 38 | // int character, |
| 39 | // size_t num_bytes); |
| 40 | // |
| 41 | // Copy c into the first n bytes of s. |
| 42 | // Returns buffer, a copy of the destination pointer. |
| 43 | // |
| 44 | |
| 45 | TEST(Memset, EmptyCase) { |
| 46 | std::array<char, 5> arr{'h', 'e', 'l', 'l', 'o'}; |
| 47 | void* ret = memset(arr.data(), 0, 0); |
| 48 | |
| 49 | // Destination buffer returned. |
| 50 | EXPECT_EQ(ret, arr.data()); |
| 51 | |
| 52 | // Destination buffer untouched. |
| 53 | constexpr std::array<char, 5> kExpected{'h', 'e', 'l', 'l', 'o'}; |
| 54 | EXPECT_TRUE( |
| 55 | std::equal(arr.begin(), arr.end(), kExpected.begin(), kExpected.end())); |
| 56 | } |
| 57 | |
| 58 | TEST(Memset, OneCharacter) { |
| 59 | std::array<char, 5> arr{'h', 'e', 'l', 'l', 'o'}; |
| 60 | void* ret = memset(arr.data(), 0, 1); |
| 61 | |
| 62 | // Ensure the destination buffer is returned. |
| 63 | EXPECT_EQ(ret, arr.data()); |
| 64 | |
| 65 | // Ensure the destination buffer is untouched. |
| 66 | constexpr std::array<char, 5> kExpected{0, 'e', 'l', 'l', 'o'}; |
| 67 | EXPECT_TRUE( |
| 68 | std::equal(arr.begin(), arr.end(), kExpected.begin(), kExpected.end())); |
| 69 | } |
| 70 | |
| 71 | // Now do a detailed case with more values. Span both word sizes and alignments |
| 72 | // to ensure we hit some edge cases. |
| 73 | TEST(Memset, MultipleSizesMultipleAlignments) { |
| 74 | constexpr int kMaxBytes = 64; |
| 75 | std::array<char, kMaxBytes> arr; |
| 76 | |
| 77 | constexpr int kMaxAlignment = 16; |
| 78 | |
| 79 | // Avoid 0 sentinel to prevent interaction with uninitialized memory. |
| 80 | constexpr char kSentinel = 3; |
| 81 | constexpr char kIotaStart = kSentinel + 7; |
| 82 | |
| 83 | // Try different alignments. |
| 84 | for (int alignment = 0; alignment < kMaxAlignment; ++alignment) { |
| 85 | // Try different memset sizes. |
| 86 | for (int write_size = 0; write_size < (kMaxBytes - kMaxAlignment); |
| 87 | ++write_size) { |
| 88 | // Fill entire array with incrementing integers; starting above sentinel. |
| 89 | std::iota(arr.begin(), arr.end(), kIotaStart); |
| 90 | |
| 91 | // Memset the first write_size bytes, with our sentinel |
| 92 | void* write_head = &arr[alignment]; |
| 93 | const void* ret = memset(write_head, kSentinel, write_size); |
| 94 | |
| 95 | // Check destination buffer returned. |
| 96 | EXPECT_EQ(ret, write_head); |
| 97 | |
| 98 | for (int j = 0; j < kMaxBytes; ++j) { |
| 99 | if (j < alignment) { |
| 100 | // First part of destination buffer untouched; should match iota. |
| 101 | EXPECT_EQ(arr[j], kIotaStart + j); |
| 102 | } else if (j < alignment + write_size) { |
| 103 | // Second part is set to the sentinel value. |
| 104 | EXPECT_EQ(arr[j], kSentinel); |
| 105 | } else { |
| 106 | // Third part is back to the iota content. |
| 107 | EXPECT_EQ(arr[j], kIotaStart + j); |
| 108 | } |
| 109 | } |
| 110 | } |
| 111 | } |
| 112 | } |
| 113 | |
| 114 | } // namespace |
| 115 | } // namespace pw |