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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Simple test for a fuzzer.
// This is a sample fuzz target for a custom serialization format that uses
// a magic separator to split the input into several independent buffers.
// The fuzzer must find the input consisting of 2 subinputs: "Fuzz" and "me".
#include <cassert>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <vector>
// Splits [data,data+size) into a vector of strings using a "magic" Separator.
std::vector<std::vector<uint8_t>> SplitInput(const uint8_t *Data, size_t Size,
const uint8_t *Separator,
size_t SeparatorSize) {
std::vector<std::vector<uint8_t>> Res;
assert(SeparatorSize > 0);
auto Beg = Data;
auto End = Data + Size;
// Using memmem here. std::search may be harder for libFuzzer today.
while (const uint8_t *Pos = (const uint8_t *)memmem(Beg, End - Beg,
Separator, SeparatorSize)) {
Res.push_back({Beg, Pos});
Beg = Pos + SeparatorSize;
if (Beg < End)
Res.push_back({Beg, End});
return Res;
static volatile int *Nil = nullptr;
extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
if (Size > 10) return 0; // To make the test quick.
const uint8_t Separator[] = {0xDE, 0xAD, 0xBE, 0xEF};
auto Inputs = SplitInput(Data, Size, Separator, sizeof(Separator));
std::vector<uint8_t> Fuzz({'F', 'u', 'z', 'z'});
std::vector<uint8_t> Me({'m', 'e'});
if (Inputs.size() == 2 && Inputs[0] == Fuzz && Inputs[1] == Me)
*Nil = 42; // crash.
return 0;