[Bug c/19430] New: Missing warning

[Bug c/19430] New: Missing warning

[terra at gnome dot org]

the program below should result in a warning that "j" might be used
uninitialized.  If the "baz" call is replaced with an explicit assignment
to "j" a warning is generated as expected.

> gcc-3.4.2 -c -Wall -O2 ~/foo.c
(stunning silence)


extern int bar (int);
extern void baz (int *);

int
foo (int i)
{
  int j;

  if (bar (i)) {
    // These should do the same with respect to `j':
    baz (&j);
    // j = 1;
  } else {
  }

  return j;
}

-- 
           Summary: Missing warning
           Product: gcc
           Version: 3.4.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: terra at gnome dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: sparc-sun-solaris2.8, i586-suse-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug c/19430] Missing warning

[dnovillo at gcc dot gnu dot org]

------- Additional Comments From dnovillo at gcc dot gnu dot org  2005-01-13 20:14 -------

Confirmed.  It doesn't work on mainline either.  The warning machinery is
getting confused with the first V_MAY_DEF to j in the first call to 'bar()'.

It would probably not be too hard to fix for 4.0.


<bb 0>:
  #   j_7 = V_MAY_DEF <j_3>;
  D.1124_2 = bar (i_1);
  if (D.1124_2 != 0) goto <L0>; else goto <L1>;

<L0>:;
  #   j_8 = V_MAY_DEF <j_7>;
  baz (&j);

  # j_6 = PHI <j_7(0), j_8(1)>;
<L1>:;
  #   VUSE <j_6>;
  D.1125_4 = j;
  return D.1125_4;


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |dnovillo at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-01-13 20:14:30
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |minor
          Component|c                           |middle-end
           Keywords|                            |diagnostic
           Priority|P2                          |P3
            Summary|Missing warning             |Missing uninitialized
                   |                            |warning


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-10 02:16 -------
*** Bug 23805 has been marked as a duplicate of this bug. ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mike at codeweavers dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-10 02:17 -------
(In reply to comment #1)
> Confirmed.  It doesn't work on mainline either.  The warning machinery is
> getting confused with the first V_MAY_DEF to j in the first call to 'bar()'.
Actually the warning machinery does not work with VOPs at all.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-10 02:19 -------
(In reply to comment #3)
> (In reply to comment #1)
> > Confirmed.  It doesn't work on mainline either.  The warning machinery is
> > getting confused with the first V_MAY_DEF to j in the first call to 'bar()'.
> Actually the warning machinery does not work with VOPs at all.
I should say see PR 23805 for an example of that.
Also the extra V_MAY_DEF is coming from that fact the clobber list is not flow sensitive, see PR 23384 
for that bug.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[mike at codeweavers dot com]

------- Additional Comments From mike at codeweavers dot com  2005-09-10 08:07 -------

Simplifying things a bit:

void foo(int*);
void bar(void) { int x; if(x) foo(&x); }

gcc -c foo.c -Wall -O2 -Wuninitialized

(More stunning silence.)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-12 21:55 -------
*** Bug 23844 has been marked as a duplicate of this bug. ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marcus at jet dot franken
                   |                            |dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[pinskia at gcc dot gnu dot org]

------- Comment #13 from pinskia at gcc dot gnu dot org  2007-03-20 17:43 -------
*** Bug 31284 has been marked as a duplicate of this bug. ***


-- 

pinskia at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[skunk at iskunk dot org]

------- Comment #12 from skunk at iskunk dot org  2007-03-02 23:36 -------
Here's my minimal test case. Compile with "-O3 -Wall -c":

#include <stdio.h>

void frob(int *pi);

int main(void)
{
    int i;
    printf("i = %d\n", i);
    frob(&i);

    return 0;
}

No warning from 4.0.3 nor 4.1.2....


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[pinskia at gcc dot gnu dot org]

------- Comment #11 from pinskia at gcc dot gnu dot org  2006-09-25 22:44 -------
*** Bug 29227 has been marked as a duplicate of this bug. ***


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |debian-gcc at lists dot
                   |                            |debian dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[mike at codeweavers dot com]

------- Comment #10 from mike at codeweavers dot com  2006-03-10 15:37 -------
Can I bribe you to work on it by fixing a Wine bug in exchange? :)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[dnovillo at gcc dot gnu dot org]

------- Comment #9 from dnovillo at gcc dot gnu dot org  2006-03-10 15:31 -------

Not going to work on this problem any time soon.


-- 

dnovillo at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|dnovillo at gcc dot gnu dot |unassigned at gcc dot gnu
                   |org                         |dot org
             Status|ASSIGNED                    |NEW


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[pinskia at gcc dot gnu dot org]

------- Comment #8 from pinskia at gcc dot gnu dot org  2006-03-10 15:28 -------
(In reply to comment #7)
> An even simpler test case of this bug (tested with gcc 3.4.5):
That works correctly in 4.0.0 and above.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

[Bug middle-end/19430] Missing uninitialized warning

[ciaccio at disi dot unige dot it]

------- Comment #7 from ciaccio at disi dot unige dot it  2006-03-10 15:25 -------
An even simpler test case of this bug (tested with gcc 3.4.5):

int main( void ) {
        int rc;
        return rc;
        *&rc = 0;
}

> gcc -O -Wall program.c
(more stunning silence)

NOTE: in this example, there is no function invocation inside main().
NOTE: remove the last statement in the program, and the warning will show up.

g.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430