添加两个二进制数字字符串-C

我知道Internet上，尤其是Stack上有很多有关此问题的信息-但我仍然受阻。

给定两个二进制数字字符串-我们必须将它们的二进制和作为字符串返回。

实际上，我认为我和这个人有同样的问题：在C中填充和添加二进制字符串

但是我进行了一些添加和更改，如下所示：

    // This function validates the two strings are really representing two binary number, and we keep the size of each
int isNum(const char* num, int* sizeOfNum) {
  *sizeOfNum = 0;
  while (*num != '\0') {
    if (*num != '0' || *num != '1') {
      return 0;
    }
    *sizeOfNum += 1;
  }
  return 1;
}

char* sumOfBinString(const char* num1, const char* num2) {

    int* sizeOfNum1 = (int*)(malloc(sizeof(int));
    int* sizeOfNum2 = (int*)(malloc(sizeof(int));

    if (isNum(num1, sizeOfNum1) && isNum(num2, sizeOfNum2)) {

        if (*sizeOfNum1 > *sizeOfNum2) {
          int size = (*sizeOfNum1);
        }
        else {
          int size = (*sizeOfNum2);
        }
    }

        //This 'size' is actually the size of the longer binary number string, and plus one for the null-terminator
    char *num1Copy = (char *)malloc((size+1) * sizeof(char));
    char *num2Copy = (char *)malloc((size+1) * sizeof(char));

    int i;
    for(i = size; i >= 0; i--)
    {
      num1Copy[i] = '0';
      num2Copy[i] = '0';
    }

    for (i = *sizeOfNum1; i >= 0; i--)
      if (i == 0 && num1Copy[i]=='1') //Two's complement
        num1Copy[i] = '1';
      else
        num1Copy[size - i] = num1[*sizeOfNum1-i];

    for (i = *sizeOfNum2; i >= 0; i--)
      if (i == 0 && num2Copy[i]=='1') //Two's complement
        num2Copy[i] == '1';
      else
        num2Copy[size - i] = num2[*sizeOfNum2-i];
}

但是我不知道如何从这里继续，因为在某些情况下，进位可能会溢出，因此我需要将该数字“加”为MSB。

有人可以帮我从这里继续吗？