Demo effectiveness of coverage-guided fuzz testing with libFuzzer (https://llvm.org/docs/LibFuzzer.html#id30)

demo_libfuzzer_coverage.cxx

// Copyright (c) 2025 Sebastian Pipping <[email protected]>
// Licensed under the MIT license

#include <cstdint>
#include <signal.h>

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
  if (Size >= 1 && Data[0] == 'H') {
    if (Size >= 2 && Data[1] == 'e') {
      if (Size >= 3 && Data[2] == 'l') {
        if (Size >= 4 && Data[3] == 'l') {
          if (Size >= 5 && Data[4] == 'o') {
            if (Size >= 6 && Data[5] == ' ') {
              if (Size >= 7 && Data[6] == 'c') {
                if (Size >= 8 && Data[7] == 'o') {
                  if (Size >= 9 && Data[8] == 'v') {
                    if (Size >= 10 && Data[9] == 'e') {
                      if (Size >= 11 && Data[10] == 'r') {
                        if (Size >= 12 && Data[11] == 'a') {
                          if (Size >= 13 && Data[12] == 'g') {
                            if (Size >= 14 && Data[13] == 'e') {
                              if (Size >= 15 && Data[14] == '!') {
                                if (Size >= 16 && Data[15] == '\n') {
                                  if (Size == 16) {
                                    raise(SIGSEGV);
                                  }
                                }
                              }
                            }
                          }
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
  return 0;
}