[Bug fortran/38830] New: Add "Variable Format Expression" I/O Capability

[Bug fortran/38830] New: Add "Variable Format Expression" I/O Capability

[tom dot browder at gmail dot com]

I would like to see a new gfortran extension added so that the "Variable Format
Expression" I/O capability will be available with gfortran as it is on many
commercial compilers.  Such a capability was once proposed as an addition to
the Fortran 95 standard but was not accepted for some reason.


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           Summary: Add "Variable Format Expression" I/O Capability
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tom dot browder at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38830

[Bug fortran/38830] Add "Variable Format Expression" I/O Capability

[burnus at gcc dot gnu dot org]

------- Comment #1 from burnus at gcc dot gnu dot org  2009-01-13 20:31 -------
Needed for legacy code; internal I/O allows the same (and more powerful) albeit
a bit lengthier.

Cf. http://gcc.gnu.org/ml/fortran/2009-01/msg00167.html
and
http://coding.derkeiler.com/Archive/Fortran/comp.lang.fortran/2008-02/msg00404.html

Proposal:            http://www.j3-fortran.org/doc/year/97/97-109.txt (Dedo)
Old version:         http://www.j3-fortran.org/doc/year/96/96-071.asc (Dedo)
Simplified proposal: http://www.j3-fortran.org/doc/year/96/96-083.txt (HP)


Other compilers:

http://h21007.www2.hp.com/portal/download/files/unprot/Fortran/docs/lrm/lrm0441.htm

http://www.intel.com/software/products/compilers/docs/flin/main_for/lref_for/source_files/pghvarfm.htm

http://publib.boulder.ibm.com/infocenter/lnxpcomp/v101v121/topic/com.ibm.xlf121.linux.doc/language_ref/format.html

http://docs.sun.com/app/docs/doc/819-5263/aevnt


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38830

[Bug fortran/38830] Add "Variable Format Expression" I/O Capability

[tkoenig at gcc dot gnu dot org]

------- Comment #2 from tkoenig at gcc dot gnu dot org  2009-01-13 20:46 -------
This is a dup of PR 20618, which was closed as WONTFIX at the time.

The semantics of variable formats are very tricky (see
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20618#c1 ),
so this is hard to get right.


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tkoenig at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38830

[Bug fortran/38830] Add "Variable Format Expression" I/O Capability

[tom dot browder at gmail dot com]

------- Comment #3 from tom dot browder at gmail dot com  2009-01-14 00:10 -------
I'm sorry I didn't catch the original "bug".  I did search but missed the
obvious reference.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38830

[Bug fortran/38830] Add "Variable Format Expression" I/O Capability

[jvdelisle at gcc dot gnu dot org]

------- Comment #4 from jvdelisle at gcc dot gnu dot org  2009-01-14 03:30 -------
I propose that we close this as WONT FIX as well, for three reasons:

1)  There are other ways to do these things and it is not necessary to use
internal I/O to do it.  Character strings can be used for format strings and
they are fully addressable down to individual characters or sections within the
string, allowing one to easily assemble format strings on the fly.  The need to
do this seems obscure.

2)  Though some members of the gcc/gfortran team have and do comment to the
Fortran standards committee, we are not the standards committee.  For whatever
reasons, the committee already rejected VFEs.  It is the purpose of this
committee to discuss and make such decisions.

3)  It appears that this feature is a legacy feature. IMHO (really) it is a
feature that leads to obtuse code and possibly self modifying code.  I do not
think it promotes best practices regarding software design and programming.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38830

[Bug fortran/38830] Document lack of "Variable Format Expression" support

[fxcoudert at gcc dot gnu dot org]

------- Comment #5 from fxcoudert at gcc dot gnu dot org  2009-03-29 08:44 -------
There's consensus that we don't want to support this feature (thread starting
at http://gcc.gnu.org/ml/fortran/2009-03/msg00205.html), so we need to document
that fact and give examples of the other ways to do the same thing.


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fxcoudert at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fxcoudert at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |documentation
   Last reconfirmed|0000-00-00 00:00:00         |2009-03-29 08:44:26
               date|                            |
            Summary|Add "Variable Format        |Document lack of "Variable
                   |Expression" I/O Capability  |Format Expression" support


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38830

[Bug fortran/38830] Document lack of "Variable Format Expression" support

[fxcoudert at gcc dot gnu dot org]

------- Comment #6 from fxcoudert at gcc dot gnu dot org  2009-05-03 12:40 -------
Patch here: http://gcc.gnu.org/ml/gcc-patches/2009-05/msg00077.html


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fxcoudert at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |fxcoudert at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
           Keywords|                            |patch
   Last reconfirmed|2009-03-29 08:44:26         |2009-05-03 12:40:04
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38830

[Bug fortran/38830] Document lack of "Variable Format Expression" support

[fxcoudert at gcc dot gnu dot org]

------- Comment #7 from fxcoudert at gcc dot gnu dot org  2009-05-07 22:14 -------
Subject: Bug 38830

Author: fxcoudert
Date: Thu May  7 22:14:23 2009
New Revision: 147258

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=147258
Log:
        PR fortran/38830
        * gfortran.texi: Document that we don't support variable FORMAT
        expressions.

Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/gfortran.texi


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38830

[Bug fortran/38830] Document lack of "Variable Format Expression" support

[fxcoudert at gcc dot gnu dot org]

------- Comment #8 from fxcoudert at gcc dot gnu dot org  2009-05-07 22:15 -------
Fixed.


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fxcoudert at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38830