libc/fuzzing/stdlib/atof_differential_fuzz.cpp

   1 //===-- atof_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 atof implementation.
  10 ///
  11 //===----------------------------------------------------------------------===//
  12 #include "src/stdlib/atof.h"
  13 #include <stddef.h>
  14 #include <stdint.h>
  15 #include <stdlib.h>
  16
  17 #include "fuzzing/stdlib/StringParserOutputDiff.h"
  18
  19 // TODO: Remove this once glibc fixes hex subnormal rounding. See
  20 // https://sourceware.org/bugzilla/show_bug.cgi?id=30220
  21 #ifdef LLVM_LIBC_ATOF_DIF_FUZZ_SKIP_GLIBC_HEX_SUBNORMAL_ERR
  22 #include <ctype.h>
  23 constexpr double MIN_NORMAL = 0x1p-1022;
  24
  25 bool has_hex_prefix(const uint8_t *str) {
  26   size_t index = 0;
  27
  28   // Skip over leading whitespace
  29   while (isspace(str[index])) {
  30     ++index;
  31   }
  32   // Skip over sign
  33   if (str[index] == '-' || str[index] == '+') {
  34     ++index;
  35   }
  36   return str[index] == '0' && (tolower(str[index + 1])) == 'x';
  37 }
  38
  39 bool should_be_skipped(const uint8_t *str) {
  40   double init_result = ::atof(reinterpret_cast<const char *>(str));
  41   if (init_result < 0) {
  42     init_result = -init_result;
  43   }
  44   if (init_result < MIN_NORMAL && init_result != 0) {
  45     return has_hex_prefix(str);
  46   }
  47   return false;
  48 }
  49 #else
  50 bool should_be_skipped(const uint8_t *) { return false; }
  51 #endif // LLVM_LIBC_ATOF_DIF_FUZZ_SKIP_GLIBC_HEX_SUBNORMAL_ERR
  52
  53 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  54   uint8_t *container = new uint8_t[size + 1];
  55   if (!container)
  56     __builtin_trap();
  57   size_t i;
  58
  59   for (i = 0; i < size; ++i)
  60     container[i] = data[i];
  61   container[size] = '\0'; // Add null terminator to container.
  62
  63   if (!should_be_skipped(container)) {
  64     StringParserOutputDiff<double>(&__llvm_libc::atof, &::atof, container,
  65                                    size);
  66   }
  67   delete[] container;
  68   return 0;
  69 }