From: cgf AT cygnus DOT com (Christopher Faylor)
Subject: Re: readlink
17 Nov 1998 05:55:58 -0800
Message-ID: <19981117082650.B18240.cygnus.cygwin32.developers@cygnus.com>
References: <uaf1qdckw DOT fsf AT parvati DOT will DOT or DOT jp>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
To: Kazuhiro Fujieda <fujieda AT jaist DOT ac DOT jp>, cygwin32-developers AT cygnus DOT com

I don't believe that this patch will handle the case of
/a/b/c/d  where c and d are both symlinks.

-chris

On Tue, Nov 17, 1998 at 04:04:47PM +0900, Kazuhiro Fujieda wrote:
>The result of readlink() in Cygwin is obviously different from
>it specified by POSIX. readlink() should not follow symlinks nor
>expand to its absolute path.
>
>For example, in POSIX environment,
>$ ln -s foo bar
>$ ln -s foobar foo
>$ ls -l bar
>lrwxrwxrwx   1 fujieda  is              6 Nov 17 14:14 bar -> foo
>but in Cygwin environment,
>$ ls -l bar
>lrw-r--r--   1 fujieda  everyone       17 Nov 17 14:10 bar -> /Home/fujieda/foobar
>
>The following is the dirty patch for winsup-981111 to solve this
>problem. Notice that this patch stop setting symlink_p to -1
>because readlink() no longer use this flag.
>
>diff -u winsup-981111/fhandler.cc winsup/fhandler.cc
>--- winsup-981111/fhandler.cc	Sun Oct 25 10:21:32 1998
>+++ winsup/fhandler.cc	Mon Nov 16 18:55:21 1998
>@@ -834,7 +834,7 @@
>   if (get_file_attribute (get_win32_name (), (int *) &buf->st_mode) > 0)
>     {
>       buf->st_mode &= ~S_IFMT;
>-      if (get_symlink_p () > 0)
>+      if (get_symlink_p ())
> 	buf->st_mode |= S_IFLNK;
>       else
> 	buf->st_mode |= S_IFREG;
>@@ -848,7 +848,7 @@
> 	buf->st_mode |= STD_WBITS;
>       /* | S_IWGRP | S_IWOTH; we don't give write to group etc */
> 
>-      if (get_symlink_p () > 0)
>+      if (get_symlink_p ())
> 	buf->st_mode |= S_IFLNK;
>       else
> 	switch (GetFileType (get_handle ()))
>@@ -1098,7 +1098,7 @@
>   if (flags & O_APPEND)
>     SetFilePointer (get_handle(), 0, 0, FILE_END);
> 
>-  set_symlink_p (real_path.symlink_p > 0);
>+  set_symlink_p (real_path.symlink_p);
>   set_execable_p (real_path.exec_p);
> 
> out:
>diff -u winsup-981111/path.cc winsup/path.cc
>--- winsup-981111/path.cc	Wed Oct 28 10:36:29 1998
>+++ winsup/path.cc	Tue Nov 17 15:59:20 1998
>@@ -287,9 +287,7 @@
> 	    {
> 	      if (component == 0)
> 		{
>-		  if (follow_mode)
>-		    symlink_p = -1;
>-		  else
>+		  if (!follow_mode)
> 		    {
> 		      symlink_p = 1;	// last component of path was a symlink.
> 		      fileattr = attr;
>@@ -1606,33 +1604,27 @@
> int
> readlink (const char *path, char *buf, int buflen)
> {
>-  path_conv pathbuf (path, 1);
>+  path_conv pathbuf (path, -1);
>   if (pathbuf.error)
>     {
>       set_errno (pathbuf.error);
>-      syscall_printf ("-1 = readlink (%s, %p, %d)", path, buf, buflen);
>-      return -1;
>-    }
>-
>-  if (!pathbuf.symlink_p)
>-    return -1;
>-
>-  char *win32_name = pathbuf.get_win32 ();
>-  if (buflen >= MAX_PATH)
>-    {
>-      if (cygwin_shared->mount.conv_to_posix_path (win32_name, buf, 1))
>-	return -1;
>-    }
>-  else
>-    {
>-      char buf1[MAX_PATH];
>-      if (cygwin_shared->mount.conv_to_posix_path (win32_name, buf1, 1))
>-	return -1;
>-      strncpy (buf, buf1, buflen);
>+      goto out;
>     }
> 
>+  int len;
>+  char sym_buf[MAX_PATH];
>+  len = symlink_check_one (pathbuf.get_win32(), sym_buf, MAX_PATH,
>+			   pathbuf.fileattr, &pathbuf.exec_p,
>+			   NULL, pathbuf.known_suffix);
>   /* errno set by symlink_check_one if error */
>+  if (len <= 0)
>+      goto out;
>+
>+  strncpy (buf, sym_buf, buflen);
>   return strlen (buf);
>+out:
>+  syscall_printf ("-1 = readlink (%s, %p, %d)", path, buf, buflen);
>+  return -1;
> }
> 
> /* Mount table system calls.
>
>____
>  | AIST      Kazuhiro Fujieda <fujieda AT jaist DOT ac DOT jp>
>  | HOKURIKU  School of Information Science
>o_/ 1990      Japan Advanced Institute of Science and Technology
>

-- 
cgf AT cygnus DOT com
http://www.cygnus.com/