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SubjectRe: [iio:togreg 3/3] WARNING: Reusing the krealloc arg is almost always a bug
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(Adding Andy Whitcroft to cc's)

On Sun, 2014-03-02 at 10:11 +0100, Lars-Peter Clausen wrote:
> On 03/02/2014 03:24 AM, Fengguang Wu wrote:
> >
> > Hi Lars-Peter,
> >
> > FYI, there are new warnings show up in
> >
> > tree: git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git togreg
> > head: bdc8cda1d010887c06bd8c29564b74cd61ec0a7b
> > commit: bdc8cda1d010887c06bd8c29564b74cd61ec0a7b [3/3] iio:adc: Add Xilinx XADC driver
> >
> > scripts/checkpatch.pl 0001-iio-adc-Add-Xilinx-XADC-driver.patch
> > # many are suggestions rather than must-fix
> > WARNING: Reusing the krealloc arg is almost always a bug
> > #1220: drivers/iio/adc/xilinx-xadc-core.c:1138:
> > + indio_dev->channels = krealloc(channels, sizeof(*channels) *
> >
>
> This is actually a false positive, checkpatch thinks that
> 'indio_dev->channels' and 'channels' is the same. Added Joe to Cc.

Yeah. perl finds an $Lval match for either
foo->bar and bar for

foo->bar = krealloc(bar, 1, GFP_KERNEL);
bar = krealloc(bar, 1, GFP_KERNEL);

I can't think of a "pretty" perl way to fix this
because I'm not much of a perl guy, but maybe this
patch below works well enough.

Find all the lvals when there's a possible krealloc
reuse. Check the lvals before and after the krealloc.
Bleat if they not equal.

Andy? Got any better idea?

---
scripts/checkpatch.pl | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 91308be..7391e01 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4275,9 +4275,15 @@ sub process {

# check for krealloc arg reuse
if ($^V && $^V ge 5.10.0 &&
- $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*krealloc\s*\(\s*\1\s*,/) {
- WARN("KREALLOC_ARG_REUSE",
- "Reusing the krealloc arg is almost always a bug\n" . $herecurr);
+ $line =~ /($Lval)\s*\=\s*(?:$balanced_parens)?\s*krealloc\s*\(\s*\1\s*,/) {
+ my @line_lvals = $line =~ m/$Lval/g;
+ for my $index (1 .. $#line_lvals - 1) {
+ if ($line_lvals[$index] eq "krealloc" &&
+ $line_lvals[$index - 1] eq $line_lvals[$index + 1]) {
+ WARN("KREALLOC_ARG_REUSE",
+ "Reusing the krealloc arg is almost always a bug\n" . $herecurr);
+ }
+ }
}

# check for alloc argument mismatch



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