[Bug fortran/28004] New: Warn if intent(out) dummy variable is not set

[Bug fortran/28004] New: Warn if intent(out) dummy variable is not set

[tobias dot burnus at physik dot fu-berlin dot de]

GNU Fortran 95 (GCC) 4.2.0 20060612.

If I write a program with a intent(out) variable and this varibale is not set,
gfortran only writes:
  warning: unused variable C

Expected: Default warning like ifort/NAG f95/g95:
 In file ff.f90:7
 subroutine sub(a)
                 1
 Warning (158): INTENT(OUT) variable 'a' at (1) is never set
---
 Warning: ff.f90, line 11: INTENT(OUT) dummy argument A never set
---
fortcom: Warning: ff.f90, line 7: A dummy argument with an explicit INTENT(OUT)
declaration is not given an explicit value.   [A]
subroutine sub(a)
---------------^

Test program:
-----------------
program test
  implicit none
  real :: a
  call sub(a)
end program test

subroutine sub(a)
  implicit none
  real, intent(out) :: a
  print *,a
end subroutine sub
-----------------

If you want, you can also -Wall warn that 'a' is used before it has gotten any
value assiged. (And Fortran does not guarantee for intent(out) that the
variable is set, even if I had add an a = 4.0 before the call sub(a).)
Actually, none of the other compilers detects this at compile time, at run time
NAG f95 (-nan or -C=undefined) does.


-- 
           Summary: Warn if intent(out) dummy variable is not set
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tobias dot burnus at physik dot fu-berlin dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is not set

[pault at gcc dot gnu dot org]

------- Comment #1 from pault at gcc dot gnu dot org  2006-06-13 19:45 -------
Tobias,

I presented a patch for this problem and for detected unassigned r-values that
was rejected.  I don't know what to say; I think that it's a bug, in principle,
but the standard does not require it.

Paul


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is not set

[tobias dot burnus at physik dot fu-berlin dot de]

------- Comment #2 from tobias dot burnus at physik dot fu-berlin dot de  2006-06-14 09:17 -------
Paul,
> I presented a patch for this problem and for detected unassigned r-values that
> was rejected.  I don't know what to say; I think that it's a bug, in principle,
> but the standard does not require it.

Well, that was the reason why one should only warn. But I think it is bad
enough to valid a default warning (as the other compilers have). But I'm also
fine with -Wall.

Tobias


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is not set

[fxcoudert at gcc dot gnu dot org]

------- Comment #3 from fxcoudert at gcc dot gnu dot org  2006-11-02 09:47 -------
(In reply to comment #1)
> I presented a patch for this problem and for detected unassigned r-values that
> was rejected.  I don't know what to say; I think that it's a bug, in principle,
> but the standard does not require it.

Paul,

I looked at that bug again but couldn't find the patch you proposed. I think we
should issue a warning but not an error, because you can write code that is
still valid:

logical function foo(a, x)
  integer,intent(in) :: a
  integer,intent(out) :: x

  foo = .false.
  if (a > 0) then
    foo = .true.
    x = a
  end if
end function foo

program test
  integer :: a, x

  a = -1
  if (foo (a,x)) print *, x
end program test


-- 

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
   Last reconfirmed|0000-00-00 00:00:00         |2006-11-02 09:47:07
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is not set

[burnus at gcc dot gnu dot org]

------- Comment #4 from burnus at gcc dot gnu dot org  2006-11-03 19:59 -------
> I think we should issue a warning but not an error, because you can write code
> that is [...]
Note that you should use "contains" for the code otherwise "foo" is regarded as
real function and the program does not compile.

g95 actually gives only a warning if the variable is not set at all, it does
not give a warning, if it is only set in the if branch. So does ifort. (NAG f95
and sunf95 don't give any warning neither with assigning it in the if branch or
not assigning it at all.)

Using -Wall gfortran states that the variable "x" is not used, but a default
warning that "A dummy argument with an explicit INTENT(OUT) declaration is not
given an explicit value." is more helpful.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is not set

[tkoenig at gcc dot gnu dot org]

------- Comment #5 from tkoenig at gcc dot gnu dot org  2006-11-11 11:18 -------
Related (and maybe more relevant):

INTENT(OUT) variables become undefined on subroutine
or function entry.  We should be able to warn if
they are used:

subroutine foo(a,b)
  real, intent(out) :: a
  real, intent(out) :: b
  print *,a
  b = a
end subroutine foo


-- 

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=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is not set

[dfranke at gcc dot gnu dot org]

------- Comment #6 from dfranke at gcc dot gnu dot org  2007-07-03 21:00 -------
Mine.


-- 

dfranke at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is not set

[dfranke at gcc dot gnu dot org]

------- Comment #7 from dfranke at gcc dot gnu dot org  2007-07-03 21:06 -------
While I got the initially requested warning, ...

> INTENT(OUT) variables become undefined on subroutine
> or function entry.  We should be able to warn if
> they are used:

... this seems to generally be the same problem as PR20520 (allocatable arrays
used uninitialized without a warning)?! Do we have any means to recognize this?


-- 

dfranke at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |dfranke at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2006-11-02 09:47:07         |2007-07-03 21:06:36
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is not set

[dfranke at gcc dot gnu dot org]

------- Comment #8 from dfranke at gcc dot gnu dot org  2007-07-08 22:41 -------
Subject: Bug 28004

Author: dfranke
Date: Sun Jul  8 22:41:35 2007
New Revision: 126471

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=126471
Log:
gcc:
2007-07-08  Daniel Franke  <franke.daniel@gmail.com>

        * function.c (do_warn_unused_parameter): Do not warn if
        TREE_NO_WARNING is set.

gcc/fortran:
2007-07-08  Daniel Franke  <franke.daniel@gmail.com>

        PR fortran/24784
        PR fortran/28004
        * trans-decl.c (generate_local_decl): Adjusted warning on unused 
        dummy arguments, tell middle-end not to emit additional warnings.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/trans-decl.c
    trunk/gcc/function.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is used before being defined

[dfranke at gcc dot gnu dot org]

------- Comment #9 from dfranke at gcc dot gnu dot org  2007-07-08 22:54 -------
Partially fixed (warn if unused and thus not set).
Changed summary to reflect the remaining task.

Unassigning myself.


-- 

dfranke at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|dfranke at gcc dot gnu dot  |unassigned at gcc dot gnu
                   |org                         |dot org
             Status|ASSIGNED                    |NEW
            Summary|Warn if intent(out) dummy   |Warn if intent(out) dummy
                   |variable is not set         |variable is used before
                   |                            |being defined


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is used before being defined

[dfranke at gcc dot gnu dot org]

------- Comment #10 from dfranke at gcc dot gnu dot org  2007-07-09 12:56 -------
Related: PR31447 - "set intent(out) arguments to uninitialized"


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

[Bug fortran/28004] Warn if intent(out) dummy variable is used before being defined

[dfranke at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28004

--- Comment #11 from Daniel Franke <dfranke at gcc dot gnu.org> 2010-12-29 14:52:48 UTC ---
Also related: PR45619.