bug#48978: 28.0.50; native-comp: Error: File error Creating file with prefix

[Eli Zaretskii]

> From: No Wayman <iarchivedmywholelife@gmail.com>
> Cc: 48978@debbugs.gnu.org
> Date: Sun, 13 Jun 2021 08:51:09 -0400
> 
> > What happens if you do the following from the shell prompt:
> >
> >   $ emacs -batch -l comp -f batch-native-compile
> > /usr/share/emacs/28.0.50/lisp/progmodes/etags.el
> 
> Here we get the rest of the file-error:
> 
> Debugger entered--Lisp error: (file-error 
> "/usr/share/emacs/28.0.50/lisp/progmodes/etags.el" "Creating file 
> with prefix" "Permission denied" 
> "/usr/share/emacs/28.0.50/lisp/progmodes/etags.elc")
>   signal(file-error 
>   ("/usr/share/emacs/28.0.50/lisp/progmodes/etags.el" "Creating 
>   file with prefix" "Permission denied" 
>   "/usr/share/emacs/28.0.50/lisp/progmodes/etags.elc"))
>   comp--native-compile("/usr/share/emacs/28.0.50/lisp/progmodes/etags.el")
>   batch-native-compile()
>   command-line-1(("-l" "comp" "-f" "batch-native-compile" 
>   "/usr/share/emacs/28.0.50/lisp/progmodes/etags.el"))
>   command-line()
>   normal-top-level()
> 
> Which is obviously a permissions error.
> 
> > Also, is /usr/share/emacs/28.0.50/lisp/progmodes writable by 
> > your
> > user?
>  
> Permissions for the directory are as follows:
> 
> drwxr-xr-x 2 root root 4.0K Jun 13 08:48 
> /usr/share/emacs/28.0.50/lisp/progmodes/
> 
> ^Looks like that's the problem!

Yes, that's what I thought was happening.

> I'm using an AUR script to install Emacs.
> I see now there was a recent change to that script which modifies 
> the permissions of directories:
> 
> https://aur.archlinux.org/cgit/aur.git/commit/?h=emacs-git&id=dca21d899ec2b1390526a300c7a617a22165dbda
> 
> Willing to bet that's the cause of the error here.
> I'll contact the maintainer of that installation script.
> Thanks for the response and sorry for the noise (though, I do 
> think there may be a bug with the way that file-error is being 
> reported).

It isn't noise: Emacs shouldn't really try creating files in that
directory, not when native-compiling in the background.

Andrea, this happens because native-compilation calls
byte-compilation, which then attempts to create the temporary .elc
file in the same directory where the .el file lives.  I show the
backtrace which leads to this issue below.

Do we really need that temporary file for the purposes of
native-compilation, or could we disable its creation?  If the latter,
I think we should, because in general there's no reason to assume the
/usr/share tree is writable by unprivileged users.

Here's the backtrace I promised:

  Thread 1 hit Breakpoint 2, Fmake_temp_file_internal 
(prefix=XIL(0x8000000008cb8990), dir_flag=XIL(0), 
suffix=XIL(0x8000000005aa61ec), text=XIL(0)) at fileio.c:692
  692       CHECK_STRING (prefix);
  (gdb) pp prefix
  "d:/gnu/git/emacs/native-comp/lisp/progmodes/etags.elc"
  (gdb) pp suff
  suffix      suffix_len  suffix_p    suffixes
  (gdb) pp suffix
  ""
  (gdb) bt
  #0  Fmake_temp_file_internal (prefix=XIL(0x8000000008cb8990),
      dir_flag=XIL(0), suffix=XIL(0x8000000005aa61ec), text=XIL(0))
      at fileio.c:692
  #1  0x7140f8a7 in F6d616b652d74656d702d66696c65_make_temp_file_0 (
      par_0=-9223372036742191384, par_1=0, par_2=0, par_3=0)
     from 
d:\gnu\git\emacs\native-comp\native-lisp\28.0.50-19bbbe78\preloaded\files-1e8937b2-855151cb.eln
  #2  0x012624c7 in funcall_subr (subr=0x5ec187c, numargs=1, args=0x82d6d8)
      at eval.c:3122
  #3  0x01261e51 in Ffuncall (nargs=2, args=0x82d6d0) at eval.c:3039
  #4  0x071273ba in F627974652d636f6d70696c652d66696c65_byte_compile_file_0 (
      par_0=-9223372036743223960, par_1=0)
     from 
d:\gnu\git\emacs\native-comp\native-lisp\28.0.50-19bbbe78\bytecomp-12882072-407267f8.eln
  #5  0x0126240c in funcall_subr (subr=0xfe4668, numargs=1, args=0x82d908)
      at eval.c:3116
  #6  0x01261e51 in Ffuncall (nargs=2, args=0x82d900) at eval.c:3039
  #7  0x012ce32c in exec_byte_code (bytestr=XIL(0x8000000006abb530),
      vector=XIL(0xa000000000ff3488), maxdepth=make_fixnum(16),
      args_template=make_fixnum(257), nargs=1, args=0x82e280) at bytecode.c:632
  #8  0x01262996 in fetch_and_exec_byte_code (fun=XIL(0xa000000000ff35f0),
      syms_left=make_fixnum(257), nargs=1, args=0x82e278) at eval.c:3163
  #9  0x01262f13 in funcall_lambda (fun=XIL(0xa000000000ff35f0), nargs=1,
      arg_vector=0x82e278) at eval.c:3244
  #10 0x01261ec1 in Ffuncall (nargs=2, args=0x82e270) at eval.c:3043
  #11 0x012603c8 in Fapply (nargs=3, args=0x82e270) at eval.c:2622
  #12 0x012622f9 in funcall_subr (subr=0x1732a80 <Sapply>, numargs=3,
      args=0x82e270) at eval.c:3094
  #13 0x01261e51 in Ffuncall (nargs=4, args=0x82e268) at eval.c:3039
  #14 0x012ce32c in exec_byte_code (bytestr=XIL(0x8000000005ed74a4),
      vector=XIL(0xa000000008c00e90), maxdepth=make_fixnum(14),
      args_template=make_fixnum(385), nargs=1, args=0x82e8b0) at bytecode.c:632
  #15 0x01262996 in fetch_and_exec_byte_code (fun=XIL(0xa000000008c0b2f0),
      syms_left=make_fixnum(385), nargs=1, args=0x82e8a8) at eval.c:3163
  #16 0x01262f13 in funcall_lambda (fun=XIL(0xa000000008c0b2f0), nargs=1,
      arg_vector=0x82e8a8) at eval.c:3244
  #17 0x01261ec1 in Ffuncall (nargs=2, args=0x82e8a0) at eval.c:3043
  #18 0x06ecfb72 in F636f6d702d7370696c6c2d6c6170_comp_spill_lap_0 (
      par_0=-9223372036743223960)
     from 
d:\gnu\git\emacs\native-comp\native-lisp\28.0.50-19bbbe78\comp-7672a6ed-b8d99e2f.eln
  #19 0x012623dd in funcall_subr (subr=0x8c0b320, numargs=1, args=0x82ead8)
      at eval.c:3114
  #20 0x01261e51 in Ffuncall (nargs=2, args=0x82ead0) at eval.c:3039
  #21 0x06f2b5aa in 
F636f6d702d2d6e61746976652d636f6d70696c65_comp__native_compile_0 
(par_0=-9223372036743223960, par_1=0, par_2=0)
     from 
d:\gnu\git\emacs\native-comp\native-lisp\28.0.50-19bbbe78\comp-7672a6ed-b8d99e2f.eln
  #22 0x01262454 in funcall_subr (subr=0x6793e30, numargs=1, args=0x82ed00)
      at eval.c:3119
  #23 0x01261e51 in Ffuncall (nargs=2, args=0x82ecf8) at eval.c:3039
  #24 0x06f2cd3d in 
F62617463682d6e61746976652d636f6d70696c65_batch_native_compile_0 ()
     from 
d:\gnu\git\emacs\native-comp\native-lisp\28.0.50-19bbbe78\comp-7672a6ed-b8d99e2f.eln
  #25 0x012623c1 in funcall_subr (subr=0x8c11638, numargs=0, args=0x82efd8)
      at eval.c:3112
  #26 0x01261e51 in Ffuncall (nargs=1, args=0x82efd0) at eval.c:3039
  #27 0x06845ee1 in F636f6d6d616e642d6c696e652d31_command_line_1_0 (
      par_0=-4611686018316439424)
     from 
d:\gnu\git\emacs\native-comp\native-lisp\28.0.50-19bbbe78\preloaded\startup-bbc6ea72-6a9af975.eln
  #28 0x012623dd in funcall_subr (subr=0x5efb2ec, numargs=1, args=0x82f3e8)
      at eval.c:3114
  #29 0x01261e51 in Ffuncall (nargs=2, args=0x82f3e0) at eval.c:3039
  #30 0x0683b3a1 in F636f6d6d616e642d6c696e65_command_line_0 ()
     from 
d:\gnu\git\emacs\native-comp\native-lisp\28.0.50-19bbbe78\preloaded\startup-bbc6ea72-6a9af975.eln
  #31 0x012623c1 in funcall_subr (subr=0x5e7f38c, numargs=0, args=0x82f638)
      at eval.c:3112
  #32 0x01261e51 in Ffuncall (nargs=1, args=0x82f630) at eval.c:3039
  #33 0x0683621d in F6e6f726d616c2d746f702d6c6576656c_normal_top_level_0 ()
     from 
d:\gnu\git\emacs\native-comp\native-lisp\28.0.50-19bbbe78\preloaded\startup-bbc6ea72-6a9af975.eln
  #34 0x0125f90f in eval_sub (form=XIL(0xc000000005f5e48c)) at eval.c:2511
  #35 0x0125edc3 in Feval (form=XIL(0xc000000005f5e48c), lexical=XIL(0))
      at eval.c:2343
  #36 0x01164957 in top_level_2 () at keyboard.c:1103
  #37 0x0125bde1 in internal_condition_case (bfun=0x1164924 <top_level_2>,
      handlers=XIL(0x90), hfun=0x11640d5 <cmd_error>) at eval.c:1478
  #38 0x011649d1 in top_level_1 (ignore=XIL(0)) at keyboard.c:1111
  #39 0x0125ab24 in internal_catch (tag=XIL(0xeee0),
      func=0x116495d <top_level_1>, arg=XIL(0)) at eval.c:1198
  #40 0x01164829 in command_loop () at keyboard.c:1072
  #41 0x01163b65 in recursive_edit_1 () at keyboard.c:720
  #42 0x01163dd3 in Frecursive_edit () at keyboard.c:789
  #43 0x0115f470 in main (argc=7, argv=0xa44140) at emacs.c:2298

  Lisp Backtrace:
  "make-temp-file" (0x82d6d8)
  "byte-compile-file" (0x82d908)
  0xff35f0 PVEC_COMPILED
  "apply" (0x82e270)
  "comp-spill-lap-function" (0x82e8a8)
  "comp-spill-lap" (0x82ead8)
  "comp--native-compile" (0x82ed00)
  "batch-native-compile" (0x82efd8)
  "command-line-1" (0x82f3e8)
  "command-line" (0x82f638)
  "normal-top-level" (0x82f728)