[Bug fortran/27589] New: Add compiler flag to check for uninitalized values at runtime

[Bug fortran/27589] New: Add compiler flag to check for uninitalized values at runtime

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

Currently, gfortran does not seem to have any option to catch uninitialized
variables at run time.

Example (from http://www.polyhedron.com/pb05/linux/diagnose.html):
--------<UNIN1>------------
        program uin1
        integer x,y,a,b
        x=y
        a=b
        print *,x,a
        b=1
        end
---------------------------

Other compilers have an options to catch those, e.g.:

ifort64-9.1 -C -check all -warn all,nodec,interfaces -gen_interfaces -traceback
-fpe0 -fpstkchk UIN1.F
./a.out
forrtl: severe (193): Run-Time Check Failure. The variable 'uin1_$Y' is being
used without being defined

NAG: f95 -C=all -C=undefined -info -g -gline UIN1.F
./a.out
Reference to undefined variable Y
Program terminated by fatal error
In UIN1, line 5 of UIN1.F


-- 
           Summary: Add compiler flag to check for uninitalized values at
                    runtime
           Product: gcc
           Version: 4.2.0
            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=27589

[Bug fortran/27589] Add compiler flag to check for uninitalized values at runtime

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

------- Comment #1 from tobias dot burnus at physik dot fu-berlin dot de  2006-05-13 14:17 -------
Post scriptum: In this case, using -Wuninitialized -O
the compiler detects that the variable is uninitialized; however, for the other
UIN*.FOR examples at polyhdron.com they are not detected at compile-time.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27589

[Bug fortran/27589] Add compiler flag to check for uninitalized values at runtime

[burnus at gcc dot gnu dot org]

------- Comment #2 from burnus at gcc dot gnu dot org  2007-03-22 22:20 -------
There are actually two run-time tests possible:

a) Check only local variables
(What to do about actual arguments to intent(in) dummy arguments? In the most
cases this is wrong, however foo(read_argument=.false.,arg=uninitialized) is
possible. Better don't check - or only optionally.)
This seems to be done by ifort's -check uninit.

b) Checking all calls, i.e. by passing additional information. This is done by
NAG f95's -C=undefined. This is more comprehensive, but makes procedures
compiled -C=undefined incompatible to those compiled without.

Ideally, gfortran should offer both options.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27589

[Bug fortran/27589] Add compiler flag to check for uninitalized values at runtime

[fxcoudert at gcc dot gnu dot org]

-- 

fxcoudert 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         |2007-04-18 07:14:46
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27589

[Bug fortran/27589] Add compiler flag to check for uninitalized values at runtime

[burnus at gcc dot gnu dot org]

------- Comment #3 from burnus at gcc dot gnu dot org  2007-06-21 16:58 -------
Dump a valid program which contains equivalence to show a harder case for the
checks (NAG f95 chokes on it).

      program main
      implicit none
      integer :: i, it, jt
      real    :: tt
      equivalence    (jt,tt)
      dimension it(10)
      do i=1,10
        tt=i
        print *, tt, jt
        it(i)=jt
      end do
      end


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27589

[Bug fortran/27589] Add compiler flag to check for uninitalized values at runtime

[burnus at gcc dot gnu dot org]

------- Comment #4 from burnus at gcc dot gnu dot org  2007-06-22 13:15 -------
(In reply to comment #3)
> Dump a valid program which contains equivalence to show a harder case for the
> checks (NAG f95 chokes on it).
Actually this is wrong according to the Section 16.5.6 of the F2003 standard:
"When a variable of a given type becomes defined, all associated
variables of different type become undefined."  There then follows an
exception that allows REAL and COMPLEX to be equivalenced and not
be undefined in this circumstance.
Thus one should check for this as well (but having a note in the documentation
for this case would make sense too.)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27589

[Bug fortran/27589] Add compiler flag to check for uninitalized values at runtime

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27589

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|24639                       |
                 CC|                            |msebor at gcc dot gnu.org

--- Comment #5 from Martin Sebor <msebor at gcc dot gnu.org> ---
Runtime checking isn't the job of -Wuninitialized so removing the dependency on
the meta bug pr27589.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639
[Bug 24639] [meta-bug] bug to track all Wuninitialized issues