[Bug 12676] New: fs/ext4/extents.c: In function ‘ext4 ext search right’: fs/ext4/extents.c:1120: warning: ‘ix’ may be used uninitialized in this function

[Bug 12676] New: fs/ext4/extents.c: In function ‘ext4 ext search right’: fs/ext4/extents.c:1120: warning: ‘ix’ may be used uninitialized in this function

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=12676

           Summary: fs/ext4/extents.c: In function
                    ‘ext4_ext_search_right’: fs/ext4/extents.c:1120:
                    warning: ‘ix’ may be used uninitialized in this
                    function
           Product: File System
           Version: 2.5
     KernelVersion: 2.6.28.4
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: ext4
        AssignedTo: fs_ext4@kernel-bugs.osdl.org
        ReportedBy: blubaustin@gmail.com


Latest working kernel version:2.6.29-rc2
Earliest failing kernel version:2.6.29rc3
Distribution:Debian Sid
Hardware Environment:Imac G3 600mhz 640MB RAM, 40GB Hard drive
Software Environment:?
Problem Description:
When compiling gets this error on Ext4 FS:
"fs/ext4/extents.c: In function ‘ext4_ext_search_right’:
fs/ext4/extents.c:1120: warning: ‘ix’ may be used uninitialized in this
function
"

Steps to reproduce:Compile kernel with Ext4


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[Bug 12676] fs/ext4/extents.c: In function ‘ext4 ext search right’: fs/ext4/extents.c:1120: warning: ‘ix’ may be used uninitialized in this function

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=12676





------- Comment #1 from sandeen@redhat.com  2009-02-09 08:10 -------
I think this is fixed upstream; you say in the bug metadata that this is
version 2.6.28.4 but the first comment says 2.6.29-rc* - which is it?


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Re: [Bug 12676] New: fs/ext4/extents.c: In function ‘ext4 ext search right’: fs/ext4/extents.c:1120: warning: ‘ix’ may be used uninitialized in this function

[Theodore Tso]

On Mon, Feb 09, 2009 at 03:15:49AM -0800, bugme-daemon@bugzilla.kernel.org wrote:
> http://bugzilla.kernel.org/show_bug.cgi?id=12676
> 
>            Summary: fs/ext4/extents.c: In function
>                     ‘ext4_ext_search_right’: fs/ext4/extents.c:1120:
>                     warning: ‘ix’ may be used uninitialized in this
>                     function

> When compiling gets this error on Ext4 FS:
> "fs/ext4/extents.c: In function ‘ext4_ext_search_right’:
> fs/ext4/extents.c:1120: warning: ‘ix’ may be used uninitialized in this
> function
> "

What version of gcc are you using to compile your kernel?  This looks
like the case of "gcc is stupid not to notice that depth must be
non-zero, so ix is always initialized".  Which doesn't seem to be the
case with gcc 4.3.2, but it might be true with an older version of
gcc.

We can shut up gcc by forcibly initializing ix, but if this is only a
problem with older gcc's, as it seems, it's probably best not to
clutter the source (and the compiled binary) with an unneeded
initialization:

	/* go up and search for index to the right */
	while (--depth >= 0) {
		ix = path[depth].p_idx;
		if (ix != EXT_LAST_INDEX(path[depth].p_hdr))
			goto got_index;
	}

	/* we've gone up to the root and found no index to the right */
	return 0;

got_index:
	/* we've found index to the right, let's
	 * follow it and find the closest allocated
	 * block to the right */
	ix++;
        ^^^^^ Gee, aren't (some verions of) gcc stupid?


	      	   	  		    	- Ted

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[Bug 12676] fs/ext4/extents.c: In function ‘ext4 ext search right’: fs/ext4/extents.c:1120: warning: ‘ix’ may be used uninitialized in this function

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=12676





------- Comment #2 from tytso@mit.edu  2009-02-10 10:21 -------
On Mon, Feb 09, 2009 at 03:15:49AM -0800, bugme-daemon@bugzilla.kernel.org
wrote:
> http://bugzilla.kernel.org/show_bug.cgi?id=12676
> 
>            Summary: fs/ext4/extents.c: In function
>                     ‘ext4_ext_search_right’: fs/ext4/extents.c:1120:
>                     warning: ‘ix’ may be used uninitialized in this
>                     function

> When compiling gets this error on Ext4 FS:
> "fs/ext4/extents.c: In function ‘ext4_ext_search_right’:
> fs/ext4/extents.c:1120: warning: ‘ix’ may be used uninitialized in this
> function
> "

What version of gcc are you using to compile your kernel?  This looks
like the case of "gcc is stupid not to notice that depth must be
non-zero, so ix is always initialized".  Which doesn't seem to be the
case with gcc 4.3.2, but it might be true with an older version of
gcc.

We can shut up gcc by forcibly initializing ix, but if this is only a
problem with older gcc's, as it seems, it's probably best not to
clutter the source (and the compiled binary) with an unneeded
initialization:

        /* go up and search for index to the right */
        while (--depth >= 0) {
                ix = path[depth].p_idx;
                if (ix != EXT_LAST_INDEX(path[depth].p_hdr))
                        goto got_index;
        }

        /* we've gone up to the root and found no index to the right */
        return 0;

got_index:
        /* we've found index to the right, let's
         * follow it and find the closest allocated
         * block to the right */
        ix++;
        ^^^^^ Gee, aren't (some verions of) gcc stupid?


                                                - Ted


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[Bug 12676] fs/ext4/extents.c: In function ‘ext4_ext_search_right’: fs/ext4/extents.c:1120: warning: ‘ix’ may be used uninitialized in this function

[bugzilla-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=12676


Theodore Tso <tytso@mit.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |tytso@mit.edu
         Resolution|                            |UNREPRODUCIBLE
         Regression|---                         |No




--- Comment #3 from Theodore Tso <tytso@mit.edu>  2009-05-19 18:36:00 ---
No response from the person filing the bug, and I don't see any compiler
warnings gcc 4.3.x, so I'm closing this bug.

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