make_temp_file__: New function.

Try to create temporary file in the most secure and portable way
possible.

Partially fixes gnu-octave#1145.

* inst/make_temp_file__.m: New function.
* inst/@sym/sym.m: Use it.
* inst/private/python_ipc_system.m: Use it.

inst/@sym/sym.m

@@ -1,5 +1,6 @@
 %% Copyright (C) 2014-2019, 2022 Colin B. Macdonald
 %% Copyright (C) 2016 Lagu
+%% Copyright (C) 2022 Alex Vong
 %%
 %% This file is part of OctSymPy.
 %%
@@ -953,7 +954,7 @@
 %! syms x
 %! y = 2*x;
 %! a = 42;
-%! myfile = tempname ();
+%! [fd, myfile] = make_temp_file__ (tempdir (), 'octsympy-myfile-');
 %! save (myfile, 'x', 'y', 'a')
 %! clear x y a
 %! load (myfile)

inst/make_temp_file__.m

@@ -0,0 +1,78 @@
+%% Copyright (C) 2022 Alex Vong
+%%
+%% This file is part of OctSymPy.
+%%
+%% OctSymPy is free software; you can redistribute it and/or modify
+%% it under the terms of the GNU General Public License as published
+%% by the Free Software Foundation; either version 3 of the License,
+%% or (at your option) any later version.
+%%
+%% This software 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 General Public License for more details.
+%%
+%% You should have received a copy of the GNU General Public
+%% License along with this software; see the file COPYING.
+%% If not, see <https://www.gnu.org/licenses/>.
+
+%% -*- texinfo -*-
+%% @documentencoding UTF-8
+%% @deftypefun {[@var{fd}, @var{filename}] =} make_temp_file__ (@var{tmpdir}, @var{prefix})
+%% Try to create temporary file in temporary directory @var{tmpdir} with prefix
+%% @var{prefix} in the most secure and portable way possible.
+%%
+%% This function is not really intended for end users.
+%%
+%% @end deftypefun
+
+
+%% This function is used in private/python_ipc_*.m
+%% Assume Python IPC is not initialized yet
+
+function [fd, filename] = make_temp_file__ (tmpdir, prefix)
+  if (exist ('OCTAVE_VERSION', 'builtin'))
+    template = [tmpdir '/' prefix 'XXXXXX'];
+    [fd, filename, msg] = mkstemp (template);
+    if (fd == -1 || isequal (filename, ''))
+      error ('make_temp_file__: cannot create temp file: %s', msg);
+    end
+
+  elseif (usejava ('jvm')) % java is required when not running octave
+    attrs = javaArray ('java.nio.file.attribute.FileAttribute', 0);
+    path = javaMethod ('createTempFile', 'java.nio.file.Files',
+                       prefix, '',
+                       attrs);
+    filename = javaMethod ('toString', path);
+    fd = fopen (filename, 'r+');
+
+  else
+    error ('make_temp_file__: cannot create temp file: please enable java');
+  end
+end
+
+
+%!test
+%! % general test
+%! [fd, filename] = make_temp_file__ (tempdir (), 'octsympy-');
+%! assert (~isempty (strfind (filename, tempdir ())));
+%! assert (~isempty (strfind (filename, 'octsympy-')));
+%! assert (mod (fd, 1) == 0 && fd > 2);
+%! s = 'hello, world';
+%! fprintf (fd, s);
+%! assert (fclose (fd) == 0);
+%! fd2 = fopen (filename);
+%! s2 = fgets (fd2);
+%! assert (isequal (s, s2));
+%! assert (fgets (fd2) == -1);
+%! assert (fclose (fd2) == 0);
+%! if (exist ('OCTAVE_VERSION', 'builtin'))
+%!   assert (unlink (filename) == 0);
+%! else
+%!   delete (filename);
+%! end
+
+%!error <cannot create temp file>
+%! if (exist ('OCTAVE_VERSION', 'builtin'))
+%!   make_temp_file__ ('/nonexistent', '');
+%! end

inst/private/python_ipc_system.m

@@ -1,4 +1,5 @@
 %% Copyright (C) 2014-2016, 2022 Colin B. Macdonald
+%% Copyright (C) 2022 Alex Vong
 %%
 %% This file is part of OctSymPy.
 %%
@@ -108,12 +109,13 @@
     %% Generate a temp .py file then execute it with system()
     % can be useful for debugging, or if "python -c" fails for you
     if (isempty (tmpfilename))
-      tmpfilename = [tempname() '_octsympytmp.py'];
+      [fd, tmpfilename] = make_temp_file__ (tempdir (), 'octsympy-tmpfile-');
       if (verbose)
         disp (['This session will use the temp file "' tmpfilename '"'])
       end
+    else
+      fd = fopen (tmpfilename, 'w');
     end
-    fd = fopen (tmpfilename, 'w');
     fprintf(fd, '# temporary autogenerated code\n\n');
     % we just added two more lines at the top
     info.prelines = info.prelines + 2;