1//===-- strcmp_fuzz.cpp ---------------------------------------------------===//
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/// Fuzzing test for llvm-libc strcmp implementation.
10///
11//===----------------------------------------------------------------------===//
12#include "src/string/strcmp.h"
13#include <stddef.h>
14#include <stdint.h>
15
16// The general structure is to take the value of the first byte, set size1 to
17// that value, and add the null terminator. size2 will then contain the rest of
18// the bytes in data.
19// For example, with inputs (data={2, 6, 4, 8, 0}, size=5):
20// size1: data[0] = 2
21// data1: {2, 6} + '\0' = {2, 6, '\0'}
22// size2: size - size1 = 3
23// data2: {4, 8, '\0'}
24extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
25 // Verify the size is at least 1 and the data is null terminated.
26 if (!size || data[size - 1] != '\0')
27 return 0;
28
29 const size_t size1 = (data[0] <= size ? data[0] : size);
30 const size_t size2 = size - size1;
31
32 // The first size will always be at least 1 since
33 // we need to append the null terminator. The second size
34 // needs to be checked since it must also contain the null
35 // terminator.
36 if (!size2)
37 return 0;
38
39 // Copy the data into new containers.
40 // Add one to data1 for null terminator.
41 uint8_t *data1 = new uint8_t[size1 + 1];
42 uint8_t *data2 = new uint8_t[size2];
43 if (!data1 || !data2)
44 __builtin_trap();
45
46 size_t i;
47 for (i = 0; i < size1; ++i)
48 data1[i] = data[i];
49 data1[size1] = '\0'; // Add null terminator to data1.
50
51 for (size_t j = 0; j < size2; ++j)
52 data2[j] = data[i++];
53
54 const char *s1 = reinterpret_cast<const char *>(data1);
55 const char *s2 = reinterpret_cast<const char *>(data2);
56 size_t k = 0;
57 // Iterate until a null terminator is hit or the character comparison is
58 // different.
59 while (s1[k] && s2[k] && s1[k] == s2[k])
60 ++k;
61
62 const unsigned char ch1 = static_cast<unsigned char>(s1[k]);
63 const unsigned char ch2 = static_cast<unsigned char>(s2[k]);
64 // The expected result should be the difference between the first non-equal
65 // characters of s1 and s2. If all characters are equal, the expected result
66 // should be '\0' - '\0' = 0.
67 if (LIBC_NAMESPACE::strcmp(left: s1, right: s2) != ch1 - ch2)
68 __builtin_trap();
69
70 // Verify reversed operands. This should be the negated value of the previous
71 // result, except of course if the previous result was zero.
72 if (LIBC_NAMESPACE::strcmp(left: s2, right: s1) != ch2 - ch1)
73 __builtin_trap();
74
75 delete[] data1;
76 delete[] data2;
77 return 0;
78}
79

source code of libc/fuzzing/string/strcmp_fuzz.cpp