[MD:1766] Bug fix of file-readable-p

[Shun-ichi GOTO <gotoh@xxxxxxxxxxx>]

Thanx for your suggestion.

>>>>> at Mon, 17 Apr 2000 14:08:32 +0200 (IST)
>>>>> eliz == Eli Zaretskii <eliz@xxxxxxxxxxxxx> said,

eliz> IIRC, `stat' fails (returns -1) on Windows for root directories.  If I'm 
eliz> right, this means that file-writable-p, as you suggest to patch it, will 
eliz> return nil for any file in the root directory of any drive.

Now I made small program to check behavior of stat() of Microsoft Visual
C/C++ 6.0 (Emacs was compiled with it) and do test on Windows 2000 and
Windows 95.

----result---------------------------------------------------------------
                           Win2000   Win95
stat.exe /		   OK, dir   OK, dir
stat.exe \		   OK, dir   OK, dir
stat.exe c:/		   OK, dir   OK, dir
stat.exe c:\		   OK, dir   OK, dir
stat.exe c:                FAIL      FAIL
stat.exe c:\autoexec.bat   OK, file  OK, file ... existing file
stat.exe c:\new-file.txt   FAIL	     FAIL     ... no file => stat() fail
stat.exe e:\               OK, dir   OK, dir  ... I have e: drive
stat.exe e:                FAIL	     FAIL
stat.exe h:\               OK, dir   OK, dir  ... h: is network drive
stat.exe h:                FAIL	     FAIL
stat.exe z:\               FAIL	     FAIL     ... I don't have Z:
stat.exe z:                FAIL	     FAIL
-------------------------------------------------------------------------


eliz> The test cases you included didn't check this case.  Could you please 
eliz> check that, both on Wndows NT and Windows 9X (if you have access to it) 
eliz> and see if this problem indeed exists?

And I did additional test on original NT Emacs and patched one.
Both emacs make same result except non-existant drive.
I think that the patch works well.

----------------------------------
                                     Original   Patched
(file-writable-p "/new-file.txt")      t	   t
(file-writable-p "/rw.txt")	       t	   t
(file-writable-p "/ro.txt")	       nil	   nil
(file-writable-p "c:/new-file.txt")    t	   t
(file-writable-p "c:/rw.txt")	       t	   t
(file-writable-p "c:/ro.txt")	       nil	   nil
(file-writable-p "c:/")		       t	   t
(file-writable-p "c:")		       t	   t

(file-writable-p "e:/")		       t	   t
(file-writable-p "e:")		       t	   t
(file-writable-p "e:/rw.txt")	       t	   t
(file-writable-p "e:/ro.txt")	       nil	   nil
(file-writable-p "e:/new-file")	       t	   t

(file-writable-p "h:/")		       t	   t
(file-writable-p "h:")		       t	   t
(file-writable-p "h:/rw.txt")	       t	   t
(file-writable-p "h:/ro.txt")	       nil	   nil
(file-writable-p "h:/new-file")	       t	   t

(file-writable-p "z:/")		       t	   nil    <--- differ
(file-writable-p "z:")		       t	   nil	  <--- differ
(file-writable-p "z:/new-file.txt")    t	   nil	  <--- differ
------------------


--- Regards,
 Shun-ichi Goto  <gotoh@xxxxxxxxxxx>
   R&D Group, TAIYO Corp., Tokyo, JAPAN

#include <stdio.h>
#include <sys/stat.h>

main(int argc, char **argv)
{
    struct stat st;
    int ret;
    ret = stat( argv[1], &st );
    printf("stat(\"%s\") => %d\n", argv[1], ret);
    if ( ret < 0 ) {
	puts("stat() failed");
    } else {
	printf("%s %s directory\n",
	       argv[1],
	       ((st.st_mode & S_IFMT) == S_IFDIR)? "is": "is not");
	       
    }
}