О корректном завершении программ на с++

void quit(void) {
    if (in != NULL)
        fclose(in);
    if (out != NULL)
        fclose(out);
    //-----------------------   
    short en = 10;
    while (en--) { Beep(4000, 8); Sleep(10); }
}
 
 
//================
//================
int main(void) {
    if (atexit(quit) != 0)
        return 1;
 
    in = fopen("in.txt", "r");
    if (in == NULL)
        return 2;
    out = fopen("out.txt", "w");
    if (out == NULL)
        return 2;

size_t word_len = std::strchr(isSrc, ' ') - ptr_ch + 1;

while (!::my_isspace(*ptr_ch++)) word_len++;
word_len++;

//============================= ВЫПОЛНЕНИЕ =====================================
            AVPacket pkt;
            bool _job(true);
            while (_job) {// << ============================================================== ЦИКЛ
            av_init_packet(&pkt);

if (read_from_FIFO(out_fmt_ctx, result_audio, fifo) != 0) { av_packet_unref(&pkt); _job = false; break; }

char* sourceTxt = new char[(srcFileData.nFileSizeHigh * MAXDWORD) + srcFileData.nFileSizeLow + 1];

enum LCType {
 lc_none,  // the line is not commented
 lc_part,   // partially commented
 lc_full     // fully commented
};
 
while (true) {
 const char * s = TakeLine(src, &len);   
 if (!s) return;
 auto state = ParseLineComment(s, len, insideFlag); 
 ...
}

LCType ParseLineComment( const char * s, int len, bool insideFlag )
{
 while (len > 0) {
   
// if we're already inside comments (opened by prev lines)
// then we're interested only in "*/"  (comments end)
  if (insideFlag) {
    const char * end = Find(s, len, "*/");  // the Find is a function such as strnstr
    if (!end) return lc_full;   // keep current state
 
    insideFlag = false;
    len -= (end - s) + 2;
    s = end + 2;     // advance to next
    continue;
  }
 
// lookup both comments begin
  const char * lc1 = Find(s, len, "//");  
  const char * lc2 = Find(s, len, "/*");  
 
// check for no any comment begin
  if (!lc1 && !lc2) 
   return lc_none;
 
// choose the first start
  if (lc1 && lc2)
   if (lc1 < lc2)
    lc2 = nullptr;
   else
    lc1 = nullptr;
 
// single line 
  if (lc1) 
   return (lc1 == s) ? lc_full : lc_part;
 
// multiline
  insideFlag = true;
  len -= (lc2 - s) + 2;
  s = lc2 + 2;     // advance to next
 }
 return insideFlag ? lc_full : lc_none;  // mistake, FIXME
}