State-Changed-From-To: open-analyzed
State-Changed-By: Manu
State-Changed-When: Mon Aug 18 20:00:44 PDT 2003
State-Changed-Why:

Dear Darren,

I've been aware of the issue for a while but did not change the current
implementation as I was afraid to break existing code. This is why I've
introduced in class FILE `file_path_exists' which will only test for
existence of a symlink file as it was requested by some of our users.

I guess we could add `is_symbolic_link' in FILE so that instead of calling
update from UNIX_FILE_INFO it calls update_with_no_symlink_resolution
link instead. This one will only query using `lstat' when available.

What do you think about that?





From: Darren Hiebert <Darren_Hiebert@XonTech.com>
To: ISE Customer Support <bugs@support.eiffel.com>
Cc:  Subject: Re: EiffelBase/3513
Date: Tue, 19 Aug 2003 08:36:54 -0500 (CDT)

 > I've been aware of the issue for a while but did not change the current
 > implementation as I was afraid to break existing code. This is why I've
 > introduced in class FILE `file_path_exists' which will only test for
 > existence of a symlink file as it was requested by some of our users.
 
 Of course, any existing code is already broken, since `is_symlink'
 always returns false. `file_path_exists' is of no value is this
 context because it does not answer the question of whether or not
 the path is a symbolic link.
 
 I realize that because the file status is read only during `update',
 that file_stat() calls stat() immediately following lstat() (thus
 losing any information about the symbolic link status), and that all
 queries are merely redirected queries to the underlying status
 structure, `is_symlink' cannot possibly work.
 
 My suggestion would be to make the change below, which add a new
 run-time call similar to file_stat() that does only lstat(), and
 then have `update' make this call before file_stat() and save the
 symlink status.
 
 --- /sstb/home/hiebertd/Eiffel/PorterPackage-5.3.0620/C/run-time/file.c	2002-03-14 17:01:11.000000000 -0600
 +++ /tmp/file.c	2003-08-19 08:32:05.159875600 -0500
 @@ -912,6 +912,36 @@
  #endif
  }
  
 +rt_public void file_lstat (char *path, struct stat *buf)
 +           				/* Path name */
 +                 		/* Structure to fill in */
 +{
 +	/* This is an encapsulation of the lstat() system call. The routine either
 +	 * succeeds and returns or fails and raises the appropriate exception.
 +	 */
 +
 +	int status;			/* System call status */
 +	
 +	for (;;) {
 +		errno = 0;						/* Reset error condition */
 +#ifdef HAS_LSTAT
 +		status = lstat(path, buf);
 +#else
 +		status = stat(path, buf);		/* Get file statistics */
 +#endif
 +		if (status == -1) {				/* An error occurred */
 +			if (errno == EINTR)			/* Interrupted by signal */
 +				continue;				/* Re-issue system call */
 +			else
 +				esys();					/* Raise exception */
 +		}
 +		break;
 +	}
 +#if defined EIF_VMS && defined _VMS_V6_SOURCE
 +	buf->st_uid &= 0x0000FFFF ;		/* VMS: mask out group id */
 +#endif
 +}
 +
  rt_public EIF_INTEGER file_info (struct stat *buf, int op)
  {
  	/* Perform the field dereferencing from the appropriate stat structure,
 --- /usr/local/Eiffel5/library/base/kernel/classic/unix_file_info.e	2002-03-14 17:28:16.000000000 -0600
 +++ /tmp/unix_file_info.e	2003-08-19 08:29:51.063183000 -0500
 @@ -138,11 +138,8 @@
  			Result := file_info ($buffered_file_info, 12) /= 0
  		end
  
 -	is_symlink: BOOLEAN is
 +	is_symlink: BOOLEAN
  			-- Is file a symbolic link?
 -		do
 -			Result := file_info ($buffered_file_info, 18) /= 0
 -		end
  
  	is_fifo: BOOLEAN is
  			-- Is file a named pipe?
 @@ -252,6 +249,8 @@
  			ext_name: ANY
  		do
  			ext_name := f_name.to_c
 +			file_lstat ($ext_name, $buffered_file_info)
 +			is_symlink := file_info ($buffered_file_info, 18) /= 0
  			file_stat ($ext_name, $buffered_file_info)
  				-- Do not duplicate the file name. That way, if the file is
  				-- renamed, the name here will change accordingly and access()
 @@ -273,6 +272,12 @@
  			"C (char *, struct stat *) | %"eif_file.h%""
  		end
  
 +	file_lstat (name, stat_buf: POINTER) is
 +			-- Get information from link `name' into `stat_buf'
 +		external
 +			"C (char *, struct stat *) | %"eif_file.h%""
 +		end
 +
  	file_access (f_name: ANY; which: INTEGER): BOOLEAN is
  			-- Perform access test `which' on `f_name' using real ID.
  		external
 
 > I guess we could add `is_symbolic_link' in FILE so that instead of calling
 > update from UNIX_FILE_INFO it calls update_with_no_symlink_resolution
 > link instead. This one will only query using `lstat' when available.
 > 
 > What do you think about that?
 
 This is another possibility. But this approach still leaves
 `is_symlink' broken. Why leave a routine known to be broken? It just
 serves as a trap for others.
 
 -- 
 Darren Hiebert <Darren_Hiebert@XonTech.com>
 Phone: 256-971-2977
 Northrop Grumman Corporation