scale10_round_decimal_decoded (int e, mpn_t m, void *memory, int n)
{
  int s;
  size_t extra_zeroes;
  unsigned int abs_n;
  unsigned int abs_s;
  mp_limb_t *pow5_ptr;
  size_t pow5_len;
  unsigned int s_limbs;
  unsigned int s_bits;
  mpn_t pow5;
  mpn_t z;
  void *z_memory;
  char *digits;

  if (memory == NULL)
    return NULL;
  /* x = 2^e * m, hence
     y = round (2^e * 10^n * m) = round (2^(e+n) * 5^n * m)
       = round (2^s * 5^n * m).  */
  s = e + n;
  extra_zeroes = 0;
  /* Factor out a common power of 10 if possible.  */
  if (s > 0 && n > 0)
    {
      extra_zeroes = (s < n ? s : n);
      s -= extra_zeroes;
      n -= extra_zeroes;
    }
  /* Here y = round (2^s * 5^n * m) * 10^extra_zeroes.
     Before converting to decimal, we need to compute
     z = round (2^s * 5^n * m).  */
  /* Compute 5^|n|, possibly shifted by |s| bits if n and s have the same
     sign.  2.322 is slightly larger than log(5)/log(2).  */
  abs_n = (n >= 0 ? n : -n);
  abs_s = (s >= 0 ? s : -s);
  pow5_ptr = (mp_limb_t *) malloc (((int)(abs_n * (2.322f / GMP_LIMB_BITS)) + 1
                                    + abs_s / GMP_LIMB_BITS + 1)
                                   * sizeof (mp_limb_t));
  if (pow5_ptr == NULL)
    {
      free (memory);
      return NULL;
    }
  /* Initialize with 1.  */
  pow5_ptr[0] = 1;
  pow5_len = 1;
  /* Multiply with 5^|n|.  */
  if (abs_n > 0)
    {
      static mp_limb_t const small_pow5[13 + 1] =
        {
          1, 5, 25, 125, 625, 3125, 15625, 78125, 390625, 1953125, 9765625,
          48828125, 244140625, 1220703125
        };
      unsigned int n13;
      for (n13 = 0; n13 <= abs_n; n13 += 13)
        {
          mp_limb_t digit1 = small_pow5[n13 + 13 <= abs_n ? 13 : abs_n - n13];
          size_t j;
          mp_twolimb_t carry = 0;
          for (j = 0; j < pow5_len; j++)
            {
              mp_limb_t digit2 = pow5_ptr[j];
              carry += (mp_twolimb_t) digit1 * (mp_twolimb_t) digit2;
              pow5_ptr[j] = (mp_limb_t) carry;
              carry = carry >> GMP_LIMB_BITS;
            }
          if (carry > 0)
            pow5_ptr[pow5_len++] = (mp_limb_t) carry;
        }
    }
  s_limbs = abs_s / GMP_LIMB_BITS;
  s_bits = abs_s % GMP_LIMB_BITS;
  if (n >= 0 ? s >= 0 : s <= 0)
    {
      /* Multiply with 2^|s|.  */
      if (s_bits > 0)
        {
          mp_limb_t *ptr = pow5_ptr;
          mp_twolimb_t accu = 0;
          size_t count;
          for (count = pow5_len; count > 0; count--)
            {
              accu += (mp_twolimb_t) *ptr << s_bits;
              *ptr++ = (mp_limb_t) accu;
              accu = accu >> GMP_LIMB_BITS;
            }
          if (accu > 0)
            {
              *ptr = (mp_limb_t) accu;
              pow5_len++;
            }
        }
      if (s_limbs > 0)
        {
          size_t count;
          for (count = pow5_len; count > 0;)
            {
              count--;
              pow5_ptr[s_limbs + count] = pow5_ptr[count];
            }
          for (count = s_limbs; count > 0;)
            {
              count--;
              pow5_ptr[count] = 0;
            }
          pow5_len += s_limbs;
        }
      pow5.limbs = pow5_ptr;
      pow5.nlimbs = pow5_len;
      if (n >= 0)
        {
          /* Multiply m with pow5.  No division needed.  */
          z_memory = multiply (m, pow5, &z);
        }
      else
        {
          /* Divide m by pow5 and round.  */
          z_memory = divide (m, pow5, &z);
        }
    }
  else
    {
      pow5.limbs = pow5_ptr;
      pow5.nlimbs = pow5_len;
      if (n >= 0)
        {
          /* n >= 0, s < 0.
             Multiply m with pow5, then divide by 2^|s|.  */
          mpn_t numerator;
          mpn_t denominator;
          void *tmp_memory;
          tmp_memory = multiply (m, pow5, &numerator);
          if (tmp_memory == NULL)
            {
              free (pow5_ptr);
              free (memory);
              return NULL;
            }
          /* Construct 2^|s|.  */
          {
            mp_limb_t *ptr = pow5_ptr + pow5_len;
            size_t i;
            for (i = 0; i < s_limbs; i++)
              ptr[i] = 0;
            ptr[s_limbs] = (mp_limb_t) 1 << s_bits;
            denominator.limbs = ptr;
            denominator.nlimbs = s_limbs + 1;
          }
          z_memory = divide (numerator, denominator, &z);
          free (tmp_memory);
        }
      else
        {
          /* n < 0, s > 0.
             Multiply m with 2^s, then divide by pow5.  */
          mpn_t numerator;
          mp_limb_t *num_ptr;
          num_ptr = (mp_limb_t *) malloc ((m.nlimbs + s_limbs + 1)
                                          * sizeof (mp_limb_t));
          if (num_ptr == NULL)
            {
              free (pow5_ptr);
              free (memory);
              return NULL;
            }
          {
            mp_limb_t *destptr = num_ptr;
            {
              size_t i;
              for (i = 0; i < s_limbs; i++)
                *destptr++ = 0;
            }
            if (s_bits > 0)
              {
                const mp_limb_t *sourceptr = m.limbs;
                mp_twolimb_t accu = 0;
                size_t count;
                for (count = m.nlimbs; count > 0; count--)
                  {
                    accu += (mp_twolimb_t) *sourceptr++ << s_bits;
                    *destptr++ = (mp_limb_t) accu;
                    accu = accu >> GMP_LIMB_BITS;
                  }
                if (accu > 0)
                  *destptr++ = (mp_limb_t) accu;
              }
            else
              {
                const mp_limb_t *sourceptr = m.limbs;
                size_t count;
                for (count = m.nlimbs; count > 0; count--)
                  *destptr++ = *sourceptr++;
              }
            numerator.limbs = num_ptr;
            numerator.nlimbs = destptr - num_ptr;
          }
          z_memory = divide (numerator, pow5, &z);
          free (num_ptr);
        }
    }
  free (pow5_ptr);
  free (memory);

  /* Here y = round (x * 10^n) = z * 10^extra_zeroes.  */

  if (z_memory == NULL)
    return NULL;
  digits = convert_to_decimal (z, extra_zeroes);
  free (z_memory);
  return digits;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.