Re: Cygwin 3.5.1: unable to open output file '/cygdrive/t/tmpdir/x-01564d.o': 'Operation not permitted'

[Dan Shelton <dan.f.shelton@gmail.com>]

On Mon, 11 Mar 2024 at 17:59, Brian Inglis via Cygwin <cygwin@cygwin.com> wrote:
>
> On 2024-03-11 04:27, Roland Mainz via Cygwin wrote:
> > On Mon, Mar 11, 2024 at 8:01 AM Cedric Blancher via Cygwin
> > <cygwin@cygwin.com> wrote:
> >> On Fri, 8 Mar 2024 at 03:25, Dan Shelton via Cygwin <cygwin@cygwin.com> wrote:
> >>> I've run into a problem with clang on Cygwin 3.5.1 and 3.6. My machine
> >>> does not have much disk space left, so I switched TMPDIR to the
> >>> network drive. But clang then failed, like this:
> >>>
> >>> $ cat x.c
> >>> #include <stdio.h>
> >>> int main(int ac, char *av[]) { puts("hello world"); return 0 ; }
> >>> $ mkdir /cygdrive/t/tmpdir
> >>> $ TMPDIR=/cygdrive/t/tmpdir clang x.c
> >>> error: unable to open output file '/cygdrive/t/tmpdir/x-01564d.o':
> >>>        'Operation not permitted'
> >>> 1 error generated.
> >>>
> >>> /cygdrive/t/tmpdir/ is a clean dir.
> >>> /usr/bin/touch /cygdrive/t/tmpdir/dummy works without problems
> >>
> >> I can confirm the bug, but only for the clang version linked to
> >> Cygwin. clang version of MinGW does not show that error, so this looks
> >> like a Cygwin bug.
> >
> > I can reproduce the bug on Cygwin "CYGWIN_NT-10.0-19045
> > 3.6.0-0.73.gc2310061c66a.x86_64":
> > ---- snip ----
> > $ cat x.c
> > #include <stdio.h>
> > int main(int ac, char *av[]) { puts("hello world"); return 0 ; }
> >
> > $ TMPDIR=/cygdrive/t/tmpdir/ strace -o clang_tmpdir_on_nfs41fs.log
> > "C:\cygwin64\bin\clang-8.exe" x.c
> > error: unable to open output file '/cygdrive/t/tmpdir/x-8cb6f7.o':
> > 'Operation not permitted'
> > 1 error generated.
> > ---- snip ----
> >
> > Full strace log is at https://nrubsig.kpaste.net/ff6248c25 (I use the
> > line numbers from that site below).
> >
> > It seems starting with line 2949 this goes wrong:
> > ---- snip ----
> >    505 5069822 [main] clang-8 40295 symlink_info::check: 0x0 =
> > NtCreateFile (\??\T:\tmpdir\x-8cb6f7.o)
> >   3645 5073467 [main] clang-8 40295 symlink_info::check: not a symlink
> >    266 5073733 [main] clang-8 40295 symlink_info::check: 0 =
> > symlink.check(T:\tmpdir\x-8cb6f7.o, 0x7FFFF96E0) (mount_flags 0x4020,
> > path_flags 0x0)
> >    310 5074043 [main] clang-8 40295 path_conv::check:
> > this->path(T:\tmpdir\x-8cb6f7.o), has_acls(1)
> >    305 5074348 [main] clang-8 40295 build_fh_pc: fh 0x800027A30, dev 000000C3
> >   1441 5075789 [main] clang-8 40295 __set_errno: int
> > check_access(security_descriptor&, GENERIC_MAPPING&, ACCESS_MASK, int,
> > bool):600 setting errno 13
> >    257 5076046 [main] clang-8 40295 check_file_access: flags 0x2, ret -1
> > ---- snip ----
> >
> > So |build_fh_pc()| somehow fails with error 13... but I don't understand why...
> >
> > And then there is this weird ACL:
> > ---- snip -----
> > $ ls -l /cygdrive/t/tmpdir/x-8cb6f7.o
> > -rw------- 1 Unix_User+197608 Unix_Group+197121 0 Mar 11 11:00
> > /cygdrive/t/tmpdir/x-8cb6f7.o
> > $ getfacl /cygdrive/t/tmpdir/x-8cb6f7.o
> > # file: /cygdrive/t/tmpdir/x-8cb6f7.o
> > # owner: Unix_User+197608
> > # group: Unix_Group+197121
> > user::---
> > group::---
> > other::---
> > ---- snip ----
> >
> > /usr/bin/file, echo&&/&/usr/bin/cat can read/write that file
> > ---- snip ----
> > $ file /cygdrive/t/tmpdir/x-8cb6f7.o
> > /cygdrive/t/tmpdir/x-8cb6f7.o: empty
> > $ echo "foo" >>/cygdrive/t/tmpdir/x-8cb6f7.o
> > $ cat /cygdrive/t/tmpdir/x-8cb6f7.o
> > foo
> > ---- snip ----
> >
> > I have no idea why clang fails in this case... I need help with this one...
>
> For normal temp space behaviour under Cygwin, I found you have to:
>
> chmod   -c a+rwxt                                          /cygdrive/t/tmpdir/
> setfacl -m u::rwx,g::rwx,o::rwx,d:u::rwx,d:g::rwx,d:o::rwx /cygdrive/t/tmpdir/
>
> to set the DACLs to rwx and avoid any problems.

That does not work either.

Dan
-- 
Dan Shelton - Cluster Specialist Win/Lin/Bsd