[Bug fortran/40206] New: [gfortran] Incorrect warning with -Wuninitialized

[Bug fortran/40206] New: [gfortran] Incorrect warning with -Wuninitialized

[martin at mpa-garching dot mpg dot de]

gfortran from the current trunk gives a warning for the code below:

module fitsmod2
implicit none

contains

function char2type (char)
  character, intent(in) :: char
  integer :: char2type

  select case (char)
    case ('E','e')
      char2type=1
    case default
      char2type=-1234
  end select
end function

function fixkey (input)
  character(len=*), intent(in) :: input
  character(len=1024) fixkey

  fixkey=input
end function

end module fitsmod2

/scratch/blah5/planck/LevelS/bugrep>gfortran -v -Wuninitialized -c -O
fitsmod2.f90
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: /scratch/martin/gcc/configure
--prefix=/afs/mpa/data/martin/ugcc --with-mpfr-include=/usr/include
--with-mpfr-lib=/usr/lib --with-gmp-include=/usr/include
--with-gmp-lib=/usr/lib --enable-languages=c++,fortran
--enable-checking=release
Thread model: posix
gcc version 4.5.0 20090520 (experimental) [trunk revision 147731] (GCC) 
COLLECT_GCC_OPTIONS='-v' '-Wuninitialized' '-c' '-O' '-mtune=generic'
 /afs/mpa/data/martin/ugcc/libexec/gcc/i686-pc-linux-gnu/4.5.0/f951
fitsmod2.f90 -quiet -dumpbase fitsmod2.f90 -mtune=generic -auxbase fitsmod2 -O
-Wuninitialized -version -fintrinsic-modules-path
/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.5.0/finclude -o
/tmp/ccPgtd3C.s
GNU Fortran (GCC) version 4.5.0 20090520 (experimental) [trunk revision 147731]
(i686-pc-linux-gnu)
        compiled by GNU C version 4.5.0 20090520 (experimental) [trunk revision
147731], GMP version 4.2.1, MPFR version 2.3.2
warning: GMP header version 4.2.1 differs from library version 4.2.4.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU Fortran (GCC) version 4.5.0 20090520 (experimental) [trunk revision 147731]
(i686-pc-linux-gnu)
        compiled by GNU C version 4.5.0 20090520 (experimental) [trunk revision
147731], GMP version 4.2.1, MPFR version 2.3.2
warning: GMP header version 4.2.1 differs from library version 4.2.4.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
fitsmod2.f90: In function 'char2type':
fitsmod2.f90:23: warning: '__result_char2type' may be used uninitialized in
this function
fitsmod2.f90:23: note: '__result_char2type' was declared here
COLLECT_GCC_OPTIONS='-v' '-Wuninitialized' '-c' '-O' '-mtune=generic'
 as -V -Qy -o fitsmod2.o /tmp/ccPgtd3C.s
GNU assembler version 2.18 (i686-pc-linux-gnu) using BFD version (GNU Binutils)
2.18
COMPILER_PATH=/afs/mpa/data/martin/ugcc/libexec/gcc/i686-pc-linux-gnu/4.5.0/:/afs/mpa/data/martin/ugcc/libexec/gcc/i686-pc-linux-gnu/4.5.0/:/afs/mpa/data/martin/ugcc/libexec/gcc/i686-pc-linux-gnu/:/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.5.0/:/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/:/usr/libexec/gcc/i686-pc-linux-gnu/:/usr/lib/gcc/i686-pc-linux-gnu/
LIBRARY_PATH=/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.5.0/:/afs/mpa/data/martin/ugcc/lib/gcc/i686-pc-linux-gnu/4.5.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-Wuninitialized' '-c' '-O' '-mtune=generic'

Several things are odd about this warning:
- the line number in question is not inside the function "char2type"
- the warning is given for a variable that is not defined by the user
- the result of "char2type" is actually initialised in all code paths


-- 
           Summary: [gfortran] Incorrect warning with -Wuninitialized
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: martin at mpa-garching dot mpg dot de
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40206

[Bug fortran/40206] [gfortran] Incorrect warning with -Wuninitialized

[burnus at gcc dot gnu dot org]

------- Comment #1 from burnus at gcc dot gnu dot org  2009-05-20 12:43 -------
The dump is the following. gfortran_select_string returns only 0, 1, or 2, but
the middle end does not know this.

Manuel, do you have an idea how to solve this?

    case_num.1 = _gfortran_select_string ((void *) &jumptable.0, 3, char, 1);
    switch (case_num.1)
      {
        case 1 ... 1:;
        case 2 ... 2:;
        __result_char2type = 1;
        goto L.1;
        case 0 ... 0:;
        __result_char2type = -1234;
        goto L.1;
      }


-- 

burnus at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu dot org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
  GCC build triplet|i686-pc-linux-gnu           |
   GCC host triplet|i686-pc-linux-gnu           |
 GCC target triplet|i686-pc-linux-gnu           |
   Last reconfirmed|0000-00-00 00:00:00         |2009-05-20 12:43:26
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40206

[Bug fortran/40206] [gfortran] Incorrect warning with -Wuninitialized

[dfranke at gcc dot gnu dot org]

------- Comment #2 from dfranke at gcc dot gnu dot org  2009-05-20 12:48 -------
I'd suspect this to be a related to Jakub's recent changes applied for PR39666
(i.e. r147136)? Does your testcase work for r147135?


-- 

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=40206

[Bug fortran/40206] [gfortran] Incorrect warning with -Wuninitialized

[martin at mpa-garching dot mpg dot de]

------- Comment #3 from martin at mpa-garching dot mpg dot de  2009-05-20 13:03 -------
(In reply to comment #2)
> I'd suspect this to be a related to Jakub's recent changes applied for PR39666
> (i.e. r147136)? Does your testcase work for r147135?

I cannot check this quickly. However I tried with gfortran 4.2.3 and the head
of the 4.4 branch and got similar warnings. Surprisingly, these compilers warn
about
line 22 (instead of 23), which is still wrong...


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40206

[Bug fortran/40206] [gfortran] Incorrect warning with -Wuninitialized

[manu at gcc dot gnu dot org]

------- Comment #4 from manu at gcc dot gnu dot org  2009-05-20 13:12 -------
(In reply to comment #2)
> I'd suspect this to be a related to Jakub's recent changes applied for PR39666
> (i.e. r147136)? Does your testcase work for r147135?
> 

On the contrary, I think this is a missed testcase from Jakub's changes,
because the default label is added during gimplification. Perhaps the patch of
Jakub can be extended to handle this, or the fortran FE can add the default
label in the correct place.

In addition, why gfortran does not name the variable char2type? Can you access
that variable when debugging?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40206

[Bug fortran/40206] [gfortran] Incorrect warning with -Wuninitialized

[burnus at gcc dot gnu dot org]

------- Comment #5 from burnus at gcc dot gnu dot org  2009-05-20 13:40 -------
    switch (case_num.1)
      {
        case 1 ... 1:;
        case 2 ... 2:;
        __result_char2type = 1;
        goto L.1;
        case 0 ... 0:;
        __result_char2type = -1234;
        goto L.1;
      }

Wouldn't this solved by adding a "default:" as C does for "default:" ?

> In addition, why gfortran does not name the variable char2type?

Good question. it clashes with the name of the function, but I don't know
whether that is a problem or not. In any case: you are right, it makes
debugging harder ...


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40206

[Bug fortran/40206] [gfortran] Incorrect warning with -Wuninitialized

[rguenth at gcc dot gnu dot org]

------- Comment #6 from rguenth at gcc dot gnu dot org  2009-05-20 14:14 -------
The FE should use a default label for the last case in the switch stmt.
I also think the FE does premature optimization here, but ...


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40206

[Bug fortran/40206] [gfortran] Incorrect warning with -Wuninitialized

[jakub at gcc dot gnu dot org]

------- Comment #7 from jakub at gcc dot gnu dot org  2009-05-20 14:32 -------
For all involved strings being non-array CHAR with length 1 I fail to see why
normal SWITCH_EXPR isn't used instead (though that would just be an
optimization).

The middle-end can't know the _gfortran_select_string function will never
return numbers bigger than the size of the jump table it is called with, so the
Fortran FE should help it.  If the table contains a default label, it should
use a default: case label instead of corresponding number, and if there is no
case label, but all possible strings are covered, it can pick a random case
label as the default.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40206

[Bug fortran/40206] [gfortran] Incorrect warning with -Wuninitialized

[jakub at gcc dot gnu dot org]

------- Comment #8 from jakub at gcc dot gnu dot org  2010-07-15 07:53 -------
Subject: Bug 40206

Author: jakub
Date: Thu Jul 15 07:52:51 2010
New Revision: 162209

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=162209
Log:
        PR fortran/40206
        * trans-stmt.c (gfc_trans_character_select): Always use NULL for high
        in CASE_LABEL_EXPR and use NULL for low for the default case.

        * gfortran.dg/select_char_3.f90: New test.

Added:
    trunk/gcc/testsuite/gfortran.dg/select_char_3.f90
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/trans-stmt.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40206

[Bug fortran/40206] [gfortran] Incorrect warning with -Wuninitialized

[jakub at gcc dot gnu dot org]

------- Comment #9 from jakub at gcc dot gnu dot org  2010-07-15 15:09 -------
Should be fixed now for 4.6+.


-- 

jakub at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40206