[patch, libgfortran] PR107031 - endfile truncates file at wrong position

[patch, libgfortran] PR107031 - endfile truncates file at wrong position

[Jerry D]

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Hi all,

There has been a bit of discussio on which way to go on this.

I took a look today and this trivial patch gives the behavior concluded 
on Fortran Discourse. See the bugzilla for all the relevant information.

Regresion tested on x86-64.

I will do the appropriate changelog.

OK for trunk?

Attached is a new test case and the patch here:

diff --git a/libgfortran/io/file_pos.c b/libgfortran/io/file_pos.c
index 2bc05b293f8..d169961f997 100644
--- a/libgfortran/io/file_pos.c
+++ b/libgfortran/io/file_pos.c
@@ -352,7 +352,6 @@ st_endfile (st_parameter_filepos *fpp)
           dtp.common = fpp->common;
           memset (&dtp.u.p, 0, sizeof (dtp.u.p));
           dtp.u.p.current_unit = u;
-         next_record (&dtp, 1);
         }

        unit_truncate (u, stell (u->s), &fpp->common);

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! { dg-do run }
! PR107031 Check that endfile truncates at end of record 5.
program test_truncate
    integer :: num_rec, tmp, i, nr, j
    open(10, file="in.dat", action='readwrite')

    do i=1,10
      write(10, *) i
    end do

    rewind (10)

    num_rec = 5
    i = 1
    ioerr = 0
    do while (i <= num_rec .and. ioerr == 0)
        read(10, *, iostat=ioerr) tmp
        i = i + 1
    enddo
    endfile(10)
    rewind (10)
    i = 0
    ioerr = 0
    do while (i <= num_rec + 1 .and. ioerr == 0)
      read(10, *, iostat=ioerr) j
      i = i + 1
    end do
    close(10, status='delete')
    if (i - 1 /= 5) stop 1
end program test_truncate

Re: [patch, libgfortran] PR107031 - endfile truncates file at wrong position

[Harald Anlauf]

Hi Jerry,

Am 26.03.24 um 04:18 schrieb Jerry D:
> Hi all,
>
> There has been a bit of discussio on which way to go on this.
>
> I took a look today and this trivial patch gives the behavior concluded
> on Fortran Discourse. See the bugzilla for all the relevant information.
>
> Regresion tested on x86-64.
>
> I will do the appropriate changelog.
>
> OK for trunk?
>
> Attached is a new test case and the patch here:
>
> diff --git a/libgfortran/io/file_pos.c b/libgfortran/io/file_pos.c
> index 2bc05b293f8..d169961f997 100644
> --- a/libgfortran/io/file_pos.c
> +++ b/libgfortran/io/file_pos.c
> @@ -352,7 +352,6 @@ st_endfile (st_parameter_filepos *fpp)
>            dtp.common = fpp->common;
>            memset (&dtp.u.p, 0, sizeof (dtp.u.p));
>            dtp.u.p.current_unit = u;
> -         next_record (&dtp, 1);
>          }
>
>         unit_truncate (u, stell (u->s), &fpp->common);

this is OK from my side.

Given the discussion on "dg-do  run", wouldn't this be a perfect
example where it is sufficient to run the testcase just once?

The change is in libgfortran, not in the frontend or middle-end.

Thanks for the patch!

Harald