/* Add library to list.  將動態庫信息添加到鏈表*/
      struct dlib_entry *dlib_ptr;
      for (dlib_ptr = dlibs; dlib_ptr != NULL; dlib_ptr = dlib_ptr->next)
 {
   /* Is soname already in list?  檢查SONAME記錄在鏈表中是否已存在，避免同一個庫重復添加多次*/
   if (strcmp (dlib_ptr->soname, soname) == 0)
     {
       /* Prefer a file to a link, otherwise check which one
   is newer.  
         SONAME的判定，以常規文件為優先來源，而不優先以鏈接文件作為SONAME的來源。
         */
       if ((!is_link && dlib_ptr->is_link)
    || (is_link == dlib_ptr->is_link
        && _dl_cache_libcmp (dlib_ptr->name, direntry->d_name) < 0))
  {
    /* It s newer - add it.  */
    /* Flag should be the same - sanity check.  */
    if (dlib_ptr->flag != flag)
      {
        if (dlib_ptr->flag == FLAG_ELF
     && (flag == FLAG_ELF_LIBC5 || flag == FLAG_ELF_LIBC6))
   dlib_ptr->flag = flag;
        else if ((dlib_ptr->flag == FLAG_ELF_LIBC5
    || dlib_ptr->flag == FLAG_ELF_LIBC6)
          && flag == FLAG_ELF)
   dlib_ptr->flag = flag;
        else
   error (0, 0, _("libraries %s and %s in directory %s have same soname but different type."),
          dlib_ptr->name, direntry->d_name,
          entry->path);
      }
    free (dlib_ptr->name);
    dlib_ptr->name = xstrdup (direntry->d_name);
    dlib_ptr->is_link = is_link;
    dlib_ptr->osversion = osversion;
    dlib_ptr->isa_level = isa_level;
  }
       /* Don t add this library, abort loop.  */
       /* Also free soname, since it s dynamically allocated.  */
       free (soname);
       break;
     }
 }
      /* Add the library if it s not already in.  
        如果該動態庫沒在緩存列表中，則添加到鏈表記錄中。
        這里看到，動態庫的信息分為name、SONAME、flag、是否為鏈接、os版本、isa_level這幾個方面
      */
      if (dlib_ptr == NULL)
 {
   dlib_ptr = (struct dlib_entry *)xmalloc (sizeof (struct dlib_entry));
   dlib_ptr->name = xstrdup (direntry->d_name);
   dlib_ptr->soname = soname;
   dlib_ptr->flag = flag;
   dlib_ptr->is_link = is_link;
   dlib_ptr->osversion = osversion;
   dlib_ptr->isa_level = isa_level;
   /* Add at head of list.  */
   dlib_ptr->next = dlibs;
   dlibs = dlib_ptr;
 }
    }

/* Now dlibs contains a list of all libs - add those to the cache
     and created all symbolic links.  
     dlibs 包含了指定目錄下查找到的所有動態庫信息。將用于添加到緩存，并創建軟鏈接（SONAME 文件）。
     */
  struct dlib_entry *dlib_ptr;
  for (dlib_ptr = dlibs; dlib_ptr != NULL; dlib_ptr = dlib_ptr->next)
    {
      /* The cached file name is the soname for non-glibc-hwcaps
  subdirectories (relying on symbolic links; this helps with
  library updates that change the file name), and the actual
  file for glibc-hwcaps subdirectories.  
     /etc/ld.so.cache 文件的
     */
      const char *filename;
      if (entry->hwcaps == NULL)
 {
   /* Don t create links to links.  
      不創建指向鏈接文件的鏈接。
      */
   if (dlib_ptr->is_link == 0)
     create_links (dir_name, entry->path, dlib_ptr->name,
     dlib_ptr->soname);
   filename = dlib_ptr->soname;
 }
      else
 {
   /* Do not create links in glibc-hwcaps subdirectories, but
      still log the cache addition.  
         glibc 的 hwcaps 是2.33 版本開始引入的功能，
         支持hwcaps意味著除了常規編譯的庫之外，現在還可以使用來自最新 CPU 
         的擴展 cpu 指令集來安裝庫，glibc 將自動選擇針對當前使用的
         cpu 優化的版本。ldconfig對于glibc-hwcaps子目錄下的動態庫，
         不會創建對應的SONAME，但仍會記錄記錄到/etc/ld.so.cache文件內。
         以被Linux在運行時按需使用。
         */
   if (opt_verbose)
     printf ("\t%s -> %s\n", dlib_ptr->soname, dlib_ptr->name);
   filename = dlib_ptr->name;
 }
      if (opt_build_cache)
 add_to_cache (entry->path, filename, dlib_ptr->soname,
        dlib_ptr->flag, dlib_ptr->osversion,
        dlib_ptr->isa_level, hwcap, entry->hwcaps);
    }

add_to_cache (entry->path, filename, dlib_ptr->soname,
        dlib_ptr->flag, dlib_ptr->osversion,
        dlib_ptr->isa_level, hwcap, entry->hwcaps);

main() {……
    search_dirs (void)//獲取所有待查找的目錄列表
    {
      struct dir_entry *entry;
      for (entry = dir_entries; entry != NULL; entry = entry->next)
        search_dir (entry); // 進入每個目錄，查找動態庫，并記錄到鏈表中
      } 
    }
     if (opt_build_cache)//若命令行參數要求生成緩存文件
    {
      save_cache (cache_file); //保存最終的緩存結果數據到 指定的緩存文件
                               //不指定文件路徑則默認是/etc/ld.so.cache 文件。
      if (aux_cache_file)// aux_cache_file是輔助緩存文件。
     save_aux_cache (aux_cache_file);
      }
}