[Bug tree-optimization/21733] New: filecmp.c:252: warning: #n1# may be used uninitialized in this function

[Bug tree-optimization/21733] New: filecmp.c:252: warning: #n1# may be used uninitialized in this function

[olh at suse dot de]

if I understand the code flow in FileCmpCmd correctly,
the first loop will initialize n1 and n2 because e1 = e2 = 0,
and k1 && k2 is always < BSIZE.
Even if the read() will return an error, the last check
to return either TCL_ERROR or TCL_OK is not undefined.


This is from http://ozlabs.org/~paulus/dirdiff-2.1.tar.gz

/usr/lib/gcc/powerpc64-suse-linux/4.0.1/cc1 -fpreprocessed filecmp.i -quiet -dumpbase filecmp.c -auxbase filecmp -O3 -Wall -version -fPIC -o filecmp.s
GNU C version 4.0.1 20050521 (prerelease) (SUSE Linux) (powerpc64-suse-linux)
        compiled by GNU C version 4.0.1 20050521 (prerelease) (SUSE Linux).
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
filecmp.c: In function #FileCmpCmd#:
filecmp.c:252: warning: #n2# may be used uninitialized in this function
filecmp.c:252: warning: #n1# may be used uninitialized in this function

-- 
           Summary: filecmp.c:252: warning: #n1# may be used uninitialized
                    in this function
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: olh at suse dot de
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: powerpc-linux
  GCC host triplet: powerpc-linux
GCC target triplet: powerpc-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21733

[Bug tree-optimization/21733] filecmp.c:252: warning: #n1# may be used uninitialized in this function

[olh at suse dot de]

------- Additional Comments From olh at suse dot de  2005-05-24 07:48 -------
Created an attachment (id=8957)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=8957&action=view)
/tmp/filecmp.i.bz2


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21733

[Bug middle-end/21733] filecmp.c:252: warning: #n1# may be used uninitialized in this function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-24 14:29 -------
This is not a regression, oh and this is much harder to get right which is why this is a "may"/"might" 
warning.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |middle-end
           Keywords|                            |diagnostic
      Known to fail|                            |3.3.3 3.4.0 4.0.0 4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21733

[Bug middle-end/21733] filecmp.c:252: warning: #n1# may be used uninitialized in this function

[James dot Juran at baesystems dot com]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |James dot Juran at
                   |                            |baesystems dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21733

[Bug middle-end/21733] filecmp.c:252: warning: #n1# may be used uninitialized in this function

[gdr at gcc dot gnu dot org]

-- 

gdr 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         |2005-11-26 07:39:55
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21733

[Bug middle-end/21733] filecmp.c:252: warning: #n1# may be used uninitialized in this function

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2005-11-26 16:52 -------
k1=k2=0;
e1=e2=0;
for(;;)
{
  if (!e1)  if(k1<1111)
  {
    set n1
    if (n1 <0)
     {
        ....
        break;
     }
  }
  if (!e2)  if(k2<1111)
  {
    set n2
    if (n2 <0)
     {
        ....
        break;
     }
  }
}
...
if (n1 < 0 || n2 < 0)
  return 1;
L1:
return 2;

------
The problem is that "n1 < 0 || n2 < 0" is being executed in one bb and not
conditionaly


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21733

[Bug middle-end/21733] filecmp.c:252: warning: #n1# may be used uninitialized in this function

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2006-08-26 03:52 -------
This is not a target specific bug either.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  GCC build triplet|powerpc-linux               |
   GCC host triplet|powerpc-linux               |
 GCC target triplet|powerpc-linux               |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21733

[Bug middle-end/21733] filecmp.c:252: warning: #n1# may be used uninitialized in this function

[manu at gcc dot gnu dot org]

------- Comment #5 from manu at gcc dot gnu dot org  2008-08-20 11:32 -------
There is some connection with PR 36296 but perhaps they are not exactly the
same issue.


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu dot org
  BugsThisDependsOn|                            |36296


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21733