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

[Roland Mainz <roland.mainz@nrubsig.org>]

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...

----

Bye,
Roland
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