[Bug fortran/39626] New: Fortran 2008: Implement BLOCK construct

[Bug fortran/39626] New: Fortran 2008: Implement BLOCK construct

[domob at gcc dot gnu dot org]

The upcoming Fortran 2008 standard introduces the BLOCK construct which allows
to declare local variables with a limited scope inside a procedure.

This is not yet implemented by gfortran.  Some ideas and discussion here:
http://gcc.gnu.org/ml/fortran/2009-04/msg00003.html


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           Summary: Fortran 2008: Implement BLOCK construct
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: domob at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626

[Bug fortran/39626] Fortran 2008: Implement BLOCK construct

[steven at gcc dot gnu dot org]

------- Comment #1 from steven at gcc dot gnu dot org  2009-04-03 16:43 -------
This feature requires a substantial re-work of symbol handling in gfortran
(make it block based).


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steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2009-04-03 16:43:38
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626

[Bug fortran/39626] Fortran 2008: Implement BLOCK construct

[domob at gcc dot gnu dot org]

------- Comment #2 from domob at gcc dot gnu dot org  2009-08-30 10:00 -------
I'm not sure it needs really that much changes...  After all, the semantics can
probably be simulated completely via replacing the BLOCK-constructs with
contained procedures that are called where the BLOCK originally was?

That's of course not a nice implementation and I do not think we should
actually do this, but I believe that there needs not be that much change --
I'll work on this and try to find out a good way.


-- 

domob at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |domob at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2009-04-03 16:43:38         |2009-08-30 10:00:24
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626

[Bug fortran/39626] Fortran 2008: Implement BLOCK construct

[burnus at gcc dot gnu dot org]

------- Comment #3 from burnus at gcc dot gnu dot org  2009-09-10 19:10 -------
See also
http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/ee95b68bf0658433#
Especially about the fine points raised by Richard Maine


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626

[Bug fortran/39626] Fortran 2008: Implement BLOCK construct

[domob at gcc dot gnu dot org]

------- Comment #4 from domob at gcc dot gnu dot org  2009-09-28 14:49 -------
For a "basically workig" (i.e. without some of the finer details and ugly
corner cases, but handling all I would "reasonably" expect as user) patch, see
http://gcc.gnu.org/ml/fortran/2009-09/msg00255.html.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626

[Bug fortran/39626] Fortran 2008: Implement BLOCK construct

[domob at gcc dot gnu dot org]

------- Comment #5 from domob at gcc dot gnu dot org  2009-09-29 07:43 -------
Subject: Bug 39626

Author: domob
Date: Tue Sep 29 07:42:42 2009
New Revision: 152266

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=152266
Log:
2009-09-29  Daniel Kraft  <d@domob.eu>

        PR fortran/39626
        * gfortran.h (enum gfc_statement): Add ST_BLOCK and ST_END_BLOCK.
        (struct gfc_namespace): Convert flags to bit-fields and add flag
        `construct_entities' for use with BLOCK constructs.
        (enum gfc_exec_code): Add EXEC_BLOCK.
        (struct gfc_code): Add namespace field to union for EXEC_BLOCK.
        * match.h (gfc_match_block): New prototype.
        * parse.h (enum gfc_compile_state): Add COMP_BLOCK.
        * trans.h (gfc_process_block_locals): New prototype.
        (gfc_trans_deferred_vars): Made public, new prototype.
        * trans-stmt.h (gfc_trans_block_construct): New prototype.
        * decl.c (gfc_match_end): Handle END BLOCK correctly.
        (gfc_match_intent): Error if inside of BLOCK.
        (gfc_match_optional), (gfc_match_value): Ditto.
        * match.c (gfc_match_block): New routine.
        * parse.c (decode_statement): Handle BLOCK statement.
        (case_exec_markers): Add ST_BLOCK.
        (case_end): Add ST_END_BLOCK.
        (gfc_ascii_statement): Handle ST_BLOCK and ST_END_BLOCK.
        (parse_spec): Check for statements not allowed inside of BLOCK.
        (parse_block_construct): New routine.
        (parse_executable): Parse BLOCKs.
        (parse_progunit): Disallow CONTAINS in BLOCK constructs.
        * resolve.c (is_illegal_recursion): Find real container procedure and
        don't get confused by BLOCK constructs.
        (resolve_block_construct): New routine.
        (gfc_resolve_blocks), (resolve_code): Handle EXEC_BLOCK.
        * st.c (gfc_free_statement): Handle EXEC_BLOCK statements.
        * trans-decl.c (saved_local_decls): New static variable.
        (add_decl_as_local): New routine.
        (gfc_finish_var_decl): Add variable as local if inside BLOCK.
        (gfc_trans_deferred_vars): Make public.
        (gfc_process_block_locals): New routine.
        * trans-stmt.c (gfc_trans_block_construct): New routine.
        * trans.c (gfc_trans_code): Handle EXEC_BLOCK statements.

2009-09-29  Daniel Kraft  <d@domob.eu>

        PR fortran/39626
        * gfortran.dg/block_1.f08: New test.
        * gfortran.dg/block_2.f08: New test.
        * gfortran.dg/block_3.f90: New test.
        * gfortran.dg/block_4.f08: New test.
        * gfortran.dg/block_5.f08: New test.
        * gfortran.dg/block_6.f08: New test.
        * gfortran.dg/block_7.f08: New test.
        * gfortran.dg/block_8.f08: New test.

Added:
    trunk/gcc/testsuite/gfortran.dg/block_1.f08
    trunk/gcc/testsuite/gfortran.dg/block_2.f08
    trunk/gcc/testsuite/gfortran.dg/block_3.f90
    trunk/gcc/testsuite/gfortran.dg/block_4.f08
    trunk/gcc/testsuite/gfortran.dg/block_5.f08
    trunk/gcc/testsuite/gfortran.dg/block_6.f08
    trunk/gcc/testsuite/gfortran.dg/block_7.f08
    trunk/gcc/testsuite/gfortran.dg/block_8.f08
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/decl.c
    trunk/gcc/fortran/gfortran.h
    trunk/gcc/fortran/match.c
    trunk/gcc/fortran/match.h
    trunk/gcc/fortran/parse.c
    trunk/gcc/fortran/parse.h
    trunk/gcc/fortran/resolve.c
    trunk/gcc/fortran/st.c
    trunk/gcc/fortran/trans-decl.c
    trunk/gcc/fortran/trans-stmt.c
    trunk/gcc/fortran/trans-stmt.h
    trunk/gcc/fortran/trans.c
    trunk/gcc/fortran/trans.h
    trunk/gcc/testsuite/ChangeLog


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626

[Bug fortran/39626] Correctly implement details of Fortran 2008 BLOCK construct

[domob at gcc dot gnu dot org]

------- Comment #7 from domob at gcc dot gnu dot org  2009-09-29 07:49 -------
Also, Tobias mentioned (in the linked thread):

The patch looks good to me. It sometimes makes the diagnostics less
useful, e.g. for

recursive function func(i)
  integer :: i, func
  func = 1
entry func2(i)
  block
    func2 = func(1)
  end block
end function func

But the same "Unclassifiable statement" one gets if one not only removes
"(end )block" but also "recursive".


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626

[Bug fortran/39626] Correctly implement details of Fortran 2008 BLOCK construct

[domob at gcc dot gnu dot org]

------- Comment #6 from domob at gcc dot gnu dot org  2009-09-29 07:48 -------
Committed my patch linked above.  This implements "basic" BLOCK support (what I
as a user would reasonably expect it to behave) but misses a lot of finer
details; I'll keep the PR open for those.

See my mailing list message for more information, but what I've got in mind for
still missing stuff:

* handle VOLATILE and ASYNCHRONOUS as the draft standard mentions
* implement the clause requiring SAVE to not reference a common-name
* do more stuff with regards to 'construct entities' rather than "ordinary
variables", for instance the IMPLICIT handling Richard Maine mentioned in his
c.l.f post which is also the XFAIL'ed test-case block_7.f08


-- 

domob at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Fortran 2008: Implement     |Correctly implement details
                   |BLOCK construct             |of Fortran 2008 BLOCK
                   |                            |construct


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626

[Bug fortran/39626] Correctly implement details of Fortran 2008 BLOCK construct

[domob at gcc dot gnu dot org]

------- Comment #8 from domob at gcc dot gnu dot org  2010-02-10 18:26 -------
*** Bug 43019 has been marked as a duplicate of this bug. ***


-- 

domob at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626

[Bug fortran/39626] Correctly implement details of Fortran 2008 BLOCK construct

[burnus at gcc dot gnu dot org]

------- Comment #9 from burnus at gcc dot gnu dot org  2010-02-17 21:52 -------
See also http://j3-fortran.org/doc/meeting/191/10-126.txt
("Scoping unit fixes for BLOCK construct")


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39626