Mail Archives: cygwin/1999/09/11/15:25:10
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mkstemp fails with an access errror when an attempt is made to create =
more than one file using the same mkstemp template. This problem was =
reported previously by Rob Mayoff.
=20
In Rob's original report, he gives the following program that =
demonstrates the problem:
In this program, the second call to mkstemp will fail:
=20
#include <stdio.h>
#include <sys/param.h>
=20
main()
{
char path[MAXPATHLEN];
int fd, rc;
=20
sprintf(path, "/tmp/test.XXXXXX");
fd =3D mkstemp(path);
if (fd < 0) { perror("mkstemp 1"); exit(1); }
rc =3D unlink(path);
if (rc < 0) { perror("unlink"); exit(1); }
sprintf(path, "/tmp/test.XXXXXX");
fd =3D mkstemp(path);
if (fd < 0) { perror("mkstemp 2"); exit(1); }
rc =3D unlink(path);
if (rc < 0) { perror("unlink"); exit(1); }
=20
exit(0);
}
=20
The fix should be simply to treat EACCES just like EEXIST in mkstemp.
=20
I have applied a patch to the runtime source file, mktemp.c, as Rob =
suggests and=20
verified the fix. I include the patch as an attachment.
=20
John
=20
John Poplett
jpoplett AT mindspring DOT com
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<DIV><FONT size=3D2>mkstemp fails with an access errror when an attempt =
is made to=20
create more than one file using the same mkstemp template. This problem =
was=20
reported previously by Rob Mayoff.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>In Rob's original report, he gives the following =
program that=20
demonstrates the problem:</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>In this program, the second call to mkstemp will=20
fail:</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>#include <stdio.h><BR>#include=20
<sys/param.h></FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>main()<BR>{<BR> char=20
path[MAXPATHLEN];<BR> int fd,=20
rc;</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2> =
sprintf(path,=20
"/tmp/test.XXXXXX");<BR> &nb=
sp; fd=20
=3D mkstemp(path);<BR> if (fd =
< 0) {=20
perror("mkstemp 1"); exit(1);=20
}<BR> rc =3D=20
unlink(path);<BR> if (rc < =
0) {=20
perror("unlink"); exit(1);=20
}<BR> sprintf(path,=20
"/tmp/test.XXXXXX");<BR> &nb=
sp; fd=20
=3D mkstemp(path);<BR> if (fd =
< 0) {=20
perror("mkstemp 2"); exit(1);=20
}<BR> rc =3D=20
unlink(path);<BR> if (rc < =
0) {=20
perror("unlink"); exit(1); }</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2> =20
exit(0);<BR>}</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>The fix should be simply to treat EACCES just like =
EEXIST in=20
mkstemp.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>I have applied a patch to the runtime source file, =
mktemp.c,=20
as Rob suggests and </FONT></DIV>
<DIV><FONT size=3D2>verified the fix. I include the patch as an=20
attachment.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>John</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>John Poplett</FONT></DIV>
<DIV><FONT size=3D2><A=20
href=3D"mailto:jpoplett AT mindspring DOT com">jpoplett AT mindspring DOT com</A><BR></=
FONT></DIV></BODY></HTML>
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name="mktemp.c"
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filename="mktemp.c"
/* This is file MKTEMP.C */
/* This file may have been modified by DJ Delorie (Jan 1991). If so,
** these modifications are Coyright (C) 1991 DJ Delorie, 24 Kirsten Ave,
** Rochester NH, 03867-2954, USA.
*/
/*
* Copyright (c) 1987 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that: (1) source distributions retain this entire copyright
* notice and comment, and (2) distributions including binaries display
* the following acknowledgement: ``This product includes software
* developed by the University of California, Berkeley and its =
contributors''
* in the documentation or other materials provided with the =
distribution
* and in all advertising materials mentioning features or use of this
* software. Neither the name of the University nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
/*
FUNCTION
<<mktemp>>, <<mkstemp>>---generate unused file name
INDEX
mktemp
INDEX
mkstemp
INDEX
_mktemp_r
INDEX
_mkstemp_r
ANSI_SYNOPSIS
#include <stdio.h>
char *mktemp(char *<[path]>);
int mkstemp(char *<[path]>);
char *_mktemp_r(void *<[reent]>, char *<[path]>);
int *_mkstemp_r(void *<[reent]>, char *<[path]>);
TRAD_SYNOPSIS
#include <stdio.h>
char *mktemp(<[path]>)
char *<[path]>;
int mkstemp(<[path]>)
char *<[path]>;
char *_mktemp_r(<[reent]>, <[path]>)
char *<[reent]>;
char *<[path]>;
int _mkstemp_r(<[reent]>, <[path]>)
char *<[reent]>;
char *<[path]>;
DESCRIPTION
<<mktemp>> and <<mkstemp>> attempt to generate a file name that is not
yet in use for any existing file. <<mkstemp>> creates the file and=20
opens it for reading and writing; <<mktemp>> simply generates the file =
name.
You supply a simple pattern for the generated file name, as the string
at <[path]>. The pattern should be a valid filename (including path
information if you wish) ending with some number of `<<X>>'
characters. The generated filename will match the leading part of the
name you supply, with the trailing `<<X>>' characters replaced by some
combination of digits and letters.
The alternate functions <<_mktemp_r>> and <<_mkstemp_r>> are reentrant
versions. The extra argument <[reent]> is a pointer to a reentrancy
structure.
RETURNS
<<mktemp>> returns the pointer <[path]> to the modified string
representing an unused filename, unless it could not generate one, or
the pattern you provided is not suitable for a filename; in that case,
it returns <<NULL>>.
<<mkstemp>> returns a file descriptor to the newly created file,
unless it could not generate an unused filename, or the pattern you
provided is not suitable for a filename; in that case, it returns
<<-1>>.
PORTABILITY
ANSI C does not require either <<mktemp>> or <<mkstemp>>; the System
V Interface Definition requires <<mktemp>> as of Issue 2.
Supporting OS subroutines required: <<getpid>>, <<open>>, <<stat>>.
*/
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdio.h>
#include <ctype.h>
#include <reent.h>
#undef _getpid_r
#undef _open_r
#undef _stat_r
#define _getpid_r(a) getpid()
#define _open_r(a,b,c,d) open(b,c,d)
#define _stat_r(a,b,c) _stat(b,c)
static
_DEFUN (_gettemp, (ptr, path, doopen),
struct _reent *ptr _AND
char *path _AND
register int *doopen)
{
register char *start, *trv;
struct stat sbuf;
unsigned int pid;
pid =3D _getpid_r (ptr);
for (trv =3D path; *trv; ++trv) /* extra X's get set to 0's */
continue;
while (*--trv =3D=3D 'X')
{
*trv =3D (pid % 10) + '0';
pid /=3D 10;
}
/*
* Check the target directory; if you have six X's and it
* doesn't exist this runs for a *very* long time.
*/
for (start =3D trv + 1;; --trv)
{
if (trv <=3D path)
break;
if (*trv =3D=3D '/')
{
*trv =3D '\0';
if (_stat_r (ptr, path, &sbuf))
return (0);
if (!(sbuf.st_mode & S_IFDIR))
{
ptr->_errno =3D ENOTDIR;
return (0);
}
*trv =3D '/';
break;
}
}
for (;;)
{
if (doopen)
{
if ((*doopen =3D _open_r (ptr, path, O_CREAT | O_EXCL | O_RDWR, =
0600))
>=3D 0)
return 1;
#ifdef __CYGWIN32__
if (ptr->_errno !=3D EEXIST && ptr->_errno !=3D EACCES)
#else
if (ptr->_errno !=3D EEXIST)
#endif
return 0;
}
else if (_stat_r (ptr, path, &sbuf))
return (ptr->_errno =3D=3D ENOENT ? 1 : 0);
/* tricky little algorithm for backward compatibility */
for (trv =3D start;;)
{
if (!*trv)
return 0;
if (*trv =3D=3D 'z')
*trv++ =3D 'a';
else
{
if (isdigit (*trv))
*trv =3D 'a';
else
++ * trv;
break;
}
}
}
/*NOTREACHED*/
}
_DEFUN (_mkstemp_r, (ptr, path),
struct _reent *ptr _AND
char *path)
{
int fd;
return (_gettemp (ptr, path, &fd) ? fd : -1);
}
char *
_DEFUN (_mktemp_r, (ptr, path),
struct _reent *ptr _AND
char *path)
{
return (_gettemp (ptr, path, (int *) NULL) ? path : (char *) NULL);
}
#ifndef _REENT_ONLY
_DEFUN (mkstemp, (path),
char *path)
{
int fd;
return (_gettemp (_REENT, path, &fd) ? fd : -1);
}
char *
_DEFUN (mktemp, (path),
char *path)
{
return (_gettemp (_REENT, path, (int *) NULL) ? path : (char *) NULL);
}
#endif /* ! defined (_REENT_ONLY) */
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