Re: [PATCH] checkpatch: Resolve improper warning for krealloc arg reuse

From: Joe Perches
Date: Wed Jul 18 2018 - 13:47:04 EST


On Wed, 2018-07-18 at 19:25 +0530, Manish Narani wrote:
> Correct the check for reuse of krealloc. It gives false warning when a
> structure member variable name and krealloc argument name is same.
>
> For Example:
> {
> ...
> abc.def_var = krealloc(def_var, sizeof(*def_var),
> GFP_KERNEL);
> ...
> }
>
> $ ./scripts/checkpatch.pl -f file.c
>
> WARNING: Reusing the krealloc arg is almost always a bug
> + abc.def_var = krealloc(def_var, sizeof(*def_var),
>
> This patch resolves the above false warning.
>
> Signed-off-by: Manish Narani <manish.narani@xxxxxxxxxx>
> ---
> scripts/checkpatch.pl | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 447857f..db9b666 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6119,7 +6119,7 @@ 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*,/) {
> + $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*krealloc\s*\(\s*\1\s*,/ && $line !~ m/[\.|\-\>].*\s*\=\s*.*/) {
> WARN("KREALLOC_ARG_REUSE",
> "Reusing the krealloc arg is almost always a bug\n" . $herecurr);
> }

This works, though I'm not completely sure why.

Andy or anyone else: Does your perl-foo understand why?

$ cat test_krealloc.c
static int xadc_parse_dt(struct iio_dev *indio_dev, struct device_node *np,
unsigned int *conf)
{
indio_dev->channels = krealloc(channels, sizeof(*channels) *
num_channels, GFP_KERNEL);
indio_dev->channels = krealloc(indio_dev->channels, sizeof(*channels) *
num_channels, GFP_KERNEL);
}

For the patch below, the old case matches the first
$Lval above as "channels" skipping the "indio_dev->"
bit and as not "indio_dev->channels"

The modified patch below matches the first $Lval as the
expected "indio_dev->channels"
---
scripts/checkpatch.pl | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index ed4fa986e8da..59eaaede757a 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6149,7 +6149,8 @@ sub process {

# check for krealloc arg reuse
if ($perl_version_ok &&
- $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*krealloc\s*\(\s*\1\s*,/) {
+ $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*krealloc\s*\(\s*($Lval)\s*,/ &&
+ $1 eq $3) {
WARN("KREALLOC_ARG_REUSE",
"Reusing the krealloc arg is almost always a bug\n" . $herecurr);
}