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

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: [email protected]
ReportedBy: [email protected]

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

------- Comment #1 from [email protected] 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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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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http://bugzilla.kernel.org/show_bug.cgi?id=12676

------- Comment #2 from [email protected] 2009-02-10 10:21 -------

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

Theodore Tso <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------

             Status|NEW                         |RESOLVED
                 CC|                            |[email protected]
         Resolution|                            |UNREPRODUCIBLE
         Regression|---                         |No

--- Comment #3 from Theodore Tso <[email protected]> 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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