[Bug libfortran/65200] New: Handle EPERM when opening files

[Bug libfortran/65200] New: Handle EPERM when opening files

[jb at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65200

            Bug ID: 65200
           Summary: Handle EPERM when opening files
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jb at gcc dot gnu.org

In some cases at least Linux can return an EPERM rather than EACCES error in
case opening a file fails, see

https://stackoverflow.com/questions/28696539/fortran-open-call-differs-on-nfsv3-vs-nfsv4

Based on some googling, the distinction between EACCES and EPERM are something
like

- EACCESS: Insufficient privilege. E.g. do the same as root and this should
work.
- EPERM: Operation not permitted. That is, no matter the privilege level, this
isn't allowed. E.g. truncating a file opened with O_APPEND and such.

but as can be seen in the URL above, both seem to be used depending on various
details.

This should be a simple fix in io/unix.c.

[Bug libfortran/65200] Handle EPERM when opening files

[jvdelisle at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65200

Jerry DeLisle <jvdelisle at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tkoenig at gcc dot gnu.org

--- Comment #1 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> ---
*** Bug 65203 has been marked as a duplicate of this bug. ***

[Bug libfortran/65200] Handle EPERM when opening files

[jvdelisle at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65200

Jerry DeLisle <jvdelisle at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jvdelisle at gcc dot gnu.org

--- Comment #2 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> ---
>From PR65203 Thomas comment:

Currently, when encountering EACCES or EROFS upon opening, we fall back towards
opening the file read-only.

This is

a) not documented
b) surprising for some users (an inconsistency has been commented upon)
c) causes inconsistencies with NFS v4, which appears to return EPERM for a
read-only file for no reason that I can see.

The original report can be found at
http://stackoverflow.com/questions/28696539/fortran-open-call-differs-on-nfsv3-vs-nfsv4
.

My suggestion would be to a) document and c) extend the behavior to EPERM.

[Bug libfortran/65200] Handle EPERM when opening files

[jb at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65200

--- Comment #4 from Janne Blomqvist <jb at gcc dot gnu.org> ---
Suggested doc patch:

Index: gfortran.texi
===================================================================
--- gfortran.texi       (revision 221234)
+++ gfortran.texi       (working copy)
@@ -1328,6 +1328,22 @@
 also force cache validation and flushing dirty data and metadata.


+@node Files opened without an explicit ACTION= specifier
+@section Files opened without an explicit ACTION= specifier
+@cindex open, action
+
+The Fortran standard says that if an @code{OPEN} statement is executed
+without an explicit @code{ACTION=} specifier, the default value is
+processor dependent.  GNU Fortran behaves as follows:
+
+@enumerate
+@item Attempt to open the file with @code{ACTION='READWRITE'}
+@item If that fails, try to open with @code{ACTION='READ'}
+@item If that fails, try to open with @code{ACTION='WRITE'}
+@item If that fails, generate an error
+@end enumerate
+
+
 @c ---------------------------------------------------------------------
 @c Extensions
 @c ---------------------------------------------------------------------

[Bug libfortran/65200] Handle EPERM when opening files

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65200

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-03-06
     Ever confirmed|0                           |1

--- Comment #5 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Confirmed per comment 3.

[Bug libfortran/65200] Handle EPERM when opening files

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65200

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |burnus at gcc dot gnu.org

--- Comment #6 from Tobias Burnus <burnus at gcc dot gnu.org> ---
(In reply to Janne Blomqvist from comment #3)
> +      char tmpmsg[256];
>        char *path = fc_strdup (opp->file, opp->file_len);
> -      size_t msglen = opp->file_len + 51;

> +      size_t msglen = opp->file_len + 22 + 256;

> +      snprintf (msg, msglen, "Cannot open file '%s': %s", path,
> +               gf_strerror (errno, tmpmsg, 256));

How about "sizeof (tmpmsg)" instead of 256?

[Bug libfortran/65200] Handle EPERM when opening files

[jb at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65200

--- Comment #7 from Janne Blomqvist <jb at gcc dot gnu.org> ---
Author: jb
Date: Wed Mar 11 21:34:22 2015
New Revision: 221361

URL: https://gcc.gnu.org/viewcvs?rev=221361&root=gcc&view=rev
Log:
PR 65200 Handle EPERM in addition to EACCES.

gcc/fortran ChangeLog:

2015-03-11  Janne Blomqvist  <jb@gcc.gnu.org>

    PR libfortran/65200
    * gfortran.texi: Document behavior when opening files without
    explicit ACTION= specifier.

libgfortran ChangeLog:

2015-03-11  Janne Blomqvist  <jb@gcc.gnu.org>

    PR libfortran/65200
    * io/open.c (new_unit): Use gf_strerror rather than hardcoding
    error messages for different errno values.
    * io/unix.c (regular_file2): Handle EPERM in addition to EACCES.

gcc/testsuite ChangeLog:

2015-03-11  Janne Blomqvist  <jb@gcc.gnu.org>

    PR libfortran/65200
    * gfortran.dg/open_errors.f90: Update checks for iomsg string.
    * gfortran.dg/open_new_segv.f90: Fix error message pattern.


Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/gfortran.texi
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gfortran.dg/open_errors.f90
    trunk/gcc/testsuite/gfortran.dg/open_new_segv.f90
    trunk/libgfortran/ChangeLog
    trunk/libgfortran/io/open.c
    trunk/libgfortran/io/unix.c

[Bug libfortran/65200] Handle EPERM when opening files

[jb at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65200

Janne Blomqvist <jb at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #8 from Janne Blomqvist <jb at gcc dot gnu.org> ---
Fixed on trunk, closing.