[Bug fortran/39171] New: Misleading warning for negative character length

[Bug fortran/39171] New: Misleading warning for negative character length

[domob at gcc dot gnu dot org]

When compiling code with a zero character-length like this:

character(len=0) :: str
end

gfortran gives no error/warning.  But for a negative length:

character(len=-1) :: str
end

one gets the misleading message:

character(len=-1) :: str
              1
Warning: CHARACTER variable has zero length at (1)

The correct behaviour is to adjust the negative length to zero; zero itself is
fine.  Dominique suggested to print this warning instead:

Warning: CHARACTER variable xxx has a negative length,
the length has been set to zero

And instead of always printing this warning, one could make it dependend on
some -W flag.


-- 
           Summary: Misleading warning for negative character length
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          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=39171

[Bug fortran/39171] Misleading warning for negative character length

[burnus at gcc dot gnu dot org]

------- Comment #1 from burnus at gcc dot gnu dot org  2009-02-13 10:34 -------
For completeness, the F2003 standard has in "4.4.4 Character type"

"The length is a type parameter; its value is greater than or equal to zero." 

and later

"If the character length parameter value evaluates to a negative value, the
length of character entities declared is zero."

Thus len=-1  is valid and equivalent to len=0.

The warning is OK in my opinion as I cannot see any reason why one would like
to have it negative at compile-time (init expression). (Maybe generated
code/preprocessor expressions, but even then a warning might be helpful.)
Whether the warning should be on by default or only with -W... is another
question.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39171

[Bug fortran/39171] Misleading warning for negative character length

[pault at gcc dot gnu dot org]

------- Comment #2 from pault at gcc dot gnu dot org  2009-02-19 05:56 -------
Confirmed

Paul


-- 

pault 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         |2009-02-19 05:56:36
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39171

[Bug fortran/39171] Misleading warning for negative character length

[domob at gcc dot gnu dot org]

------- Comment #3 from domob at gcc dot gnu dot org  2009-12-27 09:34 -------
Will work on this, as Tobias suggested the warning could depend on -Wsurprising


-- 

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|2009-02-19 05:56:36         |2009-12-27 09:34:56
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39171

[Bug fortran/39171] Misleading warning for negative character length

[domob at gcc dot gnu dot org]

------- Comment #4 from domob at gcc dot gnu dot org  2010-02-09 10:44 -------
Subject: Bug 39171

Author: domob
Date: Tue Feb  9 10:44:33 2010
New Revision: 156620

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=156620
Log:
2010-02-09  Daniel Kraft  <d@domob.eu>

        PR fortran/39171
        * resolve.c (resolve_charlen): Change warning about negative CHARACTER
        length to be correct and issue only with -Wsurprising.
        * invoke.texi (Wsurprising): Mention this new warning that is
        turned on by -Wsurprising.

2010-02-09  Daniel Kraft  <d@domob.eu>

        PR fortran/39171
        * gfortran.dg/char_length_2.f90: Change warning expectations
accordingly
        and pass -Wsurprising as necessary.

Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/invoke.texi
    trunk/gcc/fortran/resolve.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gfortran.dg/char_length_2.f90


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39171

[Bug fortran/39171] Misleading warning for negative character length

[domob at gcc dot gnu dot org]

------- Comment #5 from domob at gcc dot gnu dot org  2010-02-09 10:45 -------
Fixed on trunk.


-- 

domob at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39171

[Bug fortran/39171] Misleading warning for negative character length

[hjl dot tools at gmail dot com]

-- 

hjl dot tools at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.5.0
            Version|unknown                     |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39171