[Bug fortran/53796] I/O INQUIRE of RECL: If not specified in OPEN, the default value should be returned (sequential access)

[jb at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53796

--- Comment #19 from Janne Blomqvist <jb at gcc dot gnu.org> ---
Author: jb
Date: Tue Nov 28 19:28:50 2017
New Revision: 255215

URL: https://gcc.gnu.org/viewcvs?rev=255215&root=gcc&view=rev
Log:
PR 53796 Improve INQUIRE(RECL=...) handling

The current F2018 draft (N2137) specifies behavior of the RECL=
specifier in the INQUIRE statement, where it previously was left as
undefined. Namely:

- If the unit is not connected, RECL= should be given the value -1.
- If the unit is connected with stream access, RECL= should be given
  the value -2.

Further, as PR 53796 describes, the handling of RECL= is poor in other
ways as well. When the recl is set to the maximum possible
(GFC_INTEGER_8_HUGE / LLONG_MAX), which it does by default except for
preconnected units, and when INQUIRE(RECL=) is used with a 4 byte
integer, the value is truncated and the 4 byte value is thus
-1. Fixing this to generate an error is a lot of work, as currently
the truncation is done by the frontend, the library sees only an 8
byte value with no indication that the frontend is going to copy it to
a 4 byte one. Instead, this patch does a bit twiddling trick such that
the truncated 4 byte value is GFC_INTEGER_4_HUGE while still being
0.99999999 * GFC_INTEGER_8_HUGE which is large enough for all
practical purposes.

Finally, the patch removes GFORTRAN_DEFAULT_RECL which was used only
for preconnected units, and instead uses the same approach as describe
above.

Regtested on x86_64-pc-linux-gnu, Ok for trunk.

gcc/fortran/ChangeLog:

2017-11-28  Janne Blomqvist  <jb@gcc.gnu.org>

        PR fortran/53796
        * gfortran.texi: Remove mentions of GFORTRAN_DEFAULT_RECL.

libgfortran/ChangeLog:

2017-11-28  Janne Blomqvist  <jb@gcc.gnu.org>

        PR fortran/53796
        * io/inquire.c (inquire_via_unit): Set recl to -1 for unconnected
        units.
        * io/io.h (default_recl): New variable.
        * io/open.c (new_unit): Set recl to default_recl for sequential,
        -2 for stream access.
        * io/transfer.c (read_block_form): Test against default_recl
        instead of DEFAULT_RECL.
        (write_block): Likewise.
        * io/unit.c (init_units): Calculate max_offset, default_recl.
        * libgfortran.h (DEFAULT_RECL): Remove.
        * runtime/environ.c: Remove GFORTRAN_DEFAULT_RECL.

gcc/testsuite/ChangeLog:

2017-11-28  Janne Blomqvist  <jb@gcc.gnu.org>

        PR fortran/53796
        * gfortran.dg/inquire_recl_f2018.f90: New test.

Added:
    trunk/gcc/testsuite/gfortran.dg/inquire_recl_f2018.f90
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/gfortran.texi
    trunk/gcc/testsuite/ChangeLog
    trunk/libgfortran/io/inquire.c
    trunk/libgfortran/io/io.h
    trunk/libgfortran/io/open.c
    trunk/libgfortran/io/transfer.c
    trunk/libgfortran/io/unit.c
    trunk/libgfortran/libgfortran.h
    trunk/libgfortran/runtime/environ.c