Function ParseNaturalNumber

tests/gtest/gtest-all.cc:1381–1417

// it here.
template <typename Integer>
bool ParseNaturalNumber(const ::std::string& str, Integer* number) {
  // Fail fast if the given string does not begin with a digit;
  // this bypasses strtoXXX's "optional leading whitespace and plus
  // or minus sign" semantics, which are undesirable here.
  if (str.empty() || !IsDigit(str[0])) {
    return false;
  }
  errno = 0;

  char* end;
  // BiggestConvertible is the largest integer type that system-provided
  // string-to-number conversion routines can return.

# if GTEST_OS_WINDOWS && !defined(__GNUC__)

  // MSVC and C++ Builder define __int64 instead of the standard long long.
  typedef unsigned __int64 BiggestConvertible;
  const BiggestConvertible parsed = _strtoui64(str.c_str(), &end, 10);

# else

  typedef unsigned long long BiggestConvertible;  // NOLINT
  const BiggestConvertible parsed = strtoull(str.c_str(), &end, 10);

# endif  // GTEST_OS_WINDOWS && !defined(__GNUC__)

  const bool parse_success = *end == '\0' && errno == 0;

  GTEST_CHECK_(sizeof(Integer) <= sizeof(parsed));

  const Integer result = static_cast<Integer>(parsed);
  if (parse_success && static_cast<BiggestConvertible>(result) == parsed) {
    *number = result;
    return true;
  }
  return false;
}
#endif  // GTEST_HAS_DEATH_TEST

// TestResult contains some private methods that should be hidden from