Patchwork [U-Boot] fs/ext2/ext2fs.c: fix warning

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Submitter Andreas Bießmann
Date June 27, 2012, 11:47 a.m.
Message ID <1340797671-22171-1-git-send-email-andreas.devel@googlemail.com>
Download mbox | patch
Permalink /patch/167627/
State Superseded
Headers show

Comments

Andreas Bießmann - June 27, 2012, 11:47 a.m.
This patch fixes following warning:
---8<---
ext2fs.c: In function 'ext2fs_read_file':
ext2fs.c:458:19: warning: 'blocknxt' may be used uninitialized in this function [-Wuninitialized]
--->8---

The warning was introduced in 436da3cd233e7166b5ce9293dbd28092cf37bcc9.

Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
cc: Jason Cooper <u-boot@lakedaemon.net>
cc: Eric Nelson <eric.nelson@boundarydevices.com>
cc: Thierry Reding <thierry.reding@avionic-design.de>
---
 fs/ext2/ext2fs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Thierry Reding - June 27, 2012, 11:55 a.m.
On Wed, Jun 27, 2012 at 01:47:51PM +0200, Andreas Bießmann wrote:
> This patch fixes following warning:
> ---8<---
> ext2fs.c: In function 'ext2fs_read_file':
> ext2fs.c:458:19: warning: 'blocknxt' may be used uninitialized in this function [-Wuninitialized]
> --->8---
> 
> The warning was introduced in 436da3cd233e7166b5ce9293dbd28092cf37bcc9.
> 
> Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
> cc: Jason Cooper <u-boot@lakedaemon.net>
> cc: Eric Nelson <eric.nelson@boundarydevices.com>
> cc: Thierry Reding <thierry.reding@avionic-design.de>
> ---
>  fs/ext2/ext2fs.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext2/ext2fs.c b/fs/ext2/ext2fs.c
> index f1fce48..40b6e6f 100644
> --- a/fs/ext2/ext2fs.c
> +++ b/fs/ext2/ext2fs.c
> @@ -440,7 +440,7 @@ int ext2fs_read_file
>  		/* grab middle blocks in one go */
>  		if (i != pos / blocksize && i != blockcnt - 1 && blockcnt > 3) {
>  			int oldblk = blknr;
> -			int blocknxt;
> +			int blocknxt = blknr;
>  			while (i < blockcnt - 1) {
>  				blocknxt = ext2fs_read_block(node, i + 1);
>  				if (blocknxt == (oldblk + 1)) {

This doesn't look quite right. The warning should go away as well if you
change the "i != blockcnt - 1" to "i < blockcnt - 1" in the condition
above. I think that'd be more appropriate, but perhaps Jason is better
qualified to comment.

Thierry
u-boot@lakedaemon.net - July 6, 2012, 2:09 p.m.
On Wed, Jun 27, 2012 at 01:55:39PM +0200, Thierry Reding wrote:
> On Wed, Jun 27, 2012 at 01:47:51PM +0200, Andreas Bießmann wrote:
> > This patch fixes following warning:
> > ---8<---
> > ext2fs.c: In function 'ext2fs_read_file':
> > ext2fs.c:458:19: warning: 'blocknxt' may be used uninitialized in this function [-Wuninitialized]
> > --->8---
> > 
> > The warning was introduced in 436da3cd233e7166b5ce9293dbd28092cf37bcc9.
> > 
> > Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
> > cc: Jason Cooper <u-boot@lakedaemon.net>
> > cc: Eric Nelson <eric.nelson@boundarydevices.com>
> > cc: Thierry Reding <thierry.reding@avionic-design.de>
> > ---
> >  fs/ext2/ext2fs.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/ext2/ext2fs.c b/fs/ext2/ext2fs.c
> > index f1fce48..40b6e6f 100644
> > --- a/fs/ext2/ext2fs.c
> > +++ b/fs/ext2/ext2fs.c
> > @@ -440,7 +440,7 @@ int ext2fs_read_file
> >  		/* grab middle blocks in one go */
> >  		if (i != pos / blocksize && i != blockcnt - 1 && blockcnt > 3) {
> >  			int oldblk = blknr;
> > -			int blocknxt;
> > +			int blocknxt = blknr;
> >  			while (i < blockcnt - 1) {
> >  				blocknxt = ext2fs_read_block(node, i + 1);
> >  				if (blocknxt == (oldblk + 1)) {
> 
> This doesn't look quite right. The warning should go away as well if you
> change the "i != blockcnt - 1" to "i < blockcnt - 1" in the condition
> above. I think that'd be more appropriate, but perhaps Jason is better
> qualified to comment.

I agree.  The compiler is rightfully complaining because there is a
scenario where blockcnt > 3 and i = blockcnt - 1.  In this case, we
would decend into the if() block, but not the while() block.  blocknxt
is used after the while() block, which would then be uninitialized.

By fixing the logic in the if() block, this can't happen.  I've Ack'd
Kim's version.

Thanks for testing, Thierry.

thx,

Jason.

Patch

diff --git a/fs/ext2/ext2fs.c b/fs/ext2/ext2fs.c
index f1fce48..40b6e6f 100644
--- a/fs/ext2/ext2fs.c
+++ b/fs/ext2/ext2fs.c
@@ -440,7 +440,7 @@  int ext2fs_read_file
 		/* grab middle blocks in one go */
 		if (i != pos / blocksize && i != blockcnt - 1 && blockcnt > 3) {
 			int oldblk = blknr;
-			int blocknxt;
+			int blocknxt = blknr;
 			while (i < blockcnt - 1) {
 				blocknxt = ext2fs_read_block(node, i + 1);
 				if (blocknxt == (oldblk + 1)) {