glibc/stdio-common/tmpdir.c

/* Copyright (C) 1999-2025 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   This file is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation, either version 2.1 of the
   License, or (at your option) any later version.

   This file is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

/* Extracted from sysdeps/posix/tempname.c.  */

#include <config.h>

/* Specification.  */
#include "tmpdir.h"

#include <stdlib.h>
#include <string.h>

#include <errno.h>
#ifndef __set_errno
# define __set_errno(Val) errno = (Val)
#endif

#include <stdio.h>
#ifndef P_tmpdir
# ifdef _P_tmpdir /* native Windows */
#  define P_tmpdir _P_tmpdir
# else
#  define P_tmpdir "/tmp"
# endif
#endif

#include <sys/stat.h>

#if defined _WIN32 && ! defined __CYGWIN__
# define WIN32_LEAN_AND_MEAN  /* avoid including junk */
# include <windows.h>
#endif

#if defined _WIN32 && ! defined __CYGWIN__
/* Don't assume that UNICODE is not defined.  */
# undef GetTempPath
# define GetTempPath GetTempPathA
#endif

#if _LIBC
# define struct_stat64 struct __stat64_t64
#else
# include "pathmax.h"
# define struct_stat64 struct stat
# define __libc_secure_getenv secure_getenv
# define __stat64_time64(path, buf) stat (path, buf)
#endif

/* Pathname support.
   ISSLASH(C)           tests whether C is a directory separator character.
 */
#if defined _WIN32 || defined __CYGWIN__ || defined __EMX__ || defined __DJGPP__
  /* Native Windows, Cygwin, OS/2, DOS */
# define ISSLASH(C) ((C) == '/' || (C) == '\\')
#else
  /* Unix */
# define ISSLASH(C) ((C) == '/')
#endif


/* Return nonzero if DIR is an existent directory.  */
static bool
direxists (const char *dir)
{
  struct_stat64 buf;
  return __stat64_time64 (dir, &buf) == 0 && S_ISDIR (buf.st_mode);
}

/* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is
   non-null and exists, uses it; otherwise uses the first of $TMPDIR,
   P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
   for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
   doesn't exist, none of the searched dirs exists, or there's not
   enough space in TMPL. */
int
__path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
	       bool try_tmpdir)
{
  const char *d;
  size_t dlen, plen;
  bool add_slash;

  if (!pfx || !pfx[0])
    {
      pfx = "file";
      plen = 4;
    }
  else
    {
      plen = strlen (pfx);
      if (plen > 5)
        plen = 5;
    }

  if (try_tmpdir)
    {
      d = __libc_secure_getenv ("TMPDIR");
      if (d != NULL && direxists (d))
        dir = d;
      else if (dir != NULL && direxists (dir))
        /* nothing */ ;
      else
        dir = NULL;
    }
  if (dir == NULL)
    {
#if defined _WIN32 && ! defined __CYGWIN__
      char dirbuf[PATH_MAX];
      DWORD retval;

      /* Find Windows temporary file directory.
         We try this before P_tmpdir because Windows defines P_tmpdir to "\\"
         and will therefore try to put all temporary files in the root
         directory (unless $TMPDIR is set).  */
      retval = GetTempPath (PATH_MAX, dirbuf);
      if (retval > 0 && retval < PATH_MAX && direxists (dirbuf))
        dir = dirbuf;
      else
#endif
      if (direxists (P_tmpdir))
        dir = P_tmpdir;
      else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
        dir = "/tmp";
      else
        {
          __set_errno (ENOENT);
          return -1;
        }
    }

  dlen = strlen (dir);
#ifdef __VMS
  add_slash = 0;
#else
  add_slash = dlen != 0 && !ISSLASH (dir[dlen - 1]);
#endif

  /* check we have room for "${dir}/${pfx}XXXXXX\0" */
  if (tmpl_len < dlen + add_slash + plen + 6 + 1)
    {
      __set_errno (EINVAL);
      return -1;
    }

  memcpy (tmpl, dir, dlen);
  sprintf (tmpl + dlen, &"/%.*sXXXXXX"[!add_slash], (int) plen, pfx);
  return 0;
}