LinuxLists.cc - [PATCH 08/12] printk: Replace strncmp with str_has

2019-07-29 16:27:21

Subject: [PATCH 08/12] printk: Replace strncmp with str_has_prefix

strncmp(str, const, len) is error-prone.
We had better use newly introduced
str_has_prefix() instead of it.

Signed-off-by: Chuhong Yuan <[email protected]>
---
kernel/printk/braille.c | 4 ++--
kernel/printk/printk.c | 6 +++---
2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c
index 1d21ebacfdb8..64f0fb8ef27d 100644
--- a/kernel/printk/braille.c
+++ b/kernel/printk/braille.c
@@ -11,10 +11,10 @@

int _braille_console_setup(char **str, char **brl_options)
{
- if (!strncmp(*str, "brl,", 4)) {
+ if (str_has_prefix(*str, "brl,")) {
*brl_options = "";
*str += 4;
- } else if (!strncmp(*str, "brl=", 4)) {
+ } else if (str_has_prefix(*str, "brl=")) {
*brl_options = *str + 4;
*str = strchr(*brl_options, ',');
if (!*str) {
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 1888f6a3b694..9e60dce4bdd5 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -121,13 +121,13 @@ static int __control_devkmsg(char *str)
if (!str)
return -EINVAL;

- if (!strncmp(str, "on", 2)) {
+ if (str_has_prefix(str, "on")) {
devkmsg_log = DEVKMSG_LOG_MASK_ON;
return 2;
- } else if (!strncmp(str, "off", 3)) {
+ } else if (str_has_prefix(str, "off")) {
devkmsg_log = DEVKMSG_LOG_MASK_OFF;
return 3;
- } else if (!strncmp(str, "ratelimit", 9)) {
+ } else if (str_has_prefix(str, "ratelimit")) {
devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
return 9;
}
--
2.20.1

2019-07-30 03:44:57

by Joe Perches

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Subject: Re: [PATCH 08/12] printk: Replace strncmp with str_has_prefix

On Mon, 2019-07-29 at 23:15 +0800, Chuhong Yuan wrote:
> strncmp(str, const, len) is error-prone.
> We had better use newly introduced
> str_has_prefix() instead of it.
[]
> diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c
[]
> @@ -11,10 +11,10 @@
>
> int _braille_console_setup(char **str, char **brl_options)
> {
> - if (!strncmp(*str, "brl,", 4)) {
> + if (str_has_prefix(*str, "brl,")) {
> *brl_options = "";
> *str += 4;
> - } else if (!strncmp(*str, "brl=", 4)) {
> + } else if (str_has_prefix(*str, "brl=")) {
> *brl_options = *str + 4;

Better to get rid of the += 4 uses too by storing the result
of str_has_prefix and using that as the addend.

Perhaps
size_t len;

if ((len = str_has_prefix(*str, "brl,"))) {
*brl_options = "";
*str += len;
} else if ((len = str_has_prefix(*str, "brl="))) {
etc...

> *str = strchr(*brl_options, ',');
> if (!*str) {
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
[]
> @@ -121,13 +121,13 @@ static int __control_devkmsg(char *str)
> if (!str)
> return -EINVAL;
>
> - if (!strncmp(str, "on", 2)) {
> + if (str_has_prefix(str, "on")) {
> devkmsg_log = DEVKMSG_LOG_MASK_ON;
> return 2;
> - } else if (!strncmp(str, "off", 3)) {
> + } else if (str_has_prefix(str, "off")) {
> devkmsg_log = DEVKMSG_LOG_MASK_OFF;
> return 3;
> - } else if (!strncmp(str, "ratelimit", 9)) {
> + } else if (str_has_prefix(str, "ratelimit")) {
> devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
> return 9;
> }

here too.

2019-08-01 15:49:28

by Chuhong Yuan

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Subject: Re: [PATCH 08/12] printk: Replace strncmp with str_has_prefix

Joe Perches <[email protected]> 于2019年7月30日周二上午8:16写道：
>
> On Mon, 2019-07-29 at 23:15 +0800, Chuhong Yuan wrote:
> > strncmp(str, const, len) is error-prone.
> > We had better use newly introduced
> > str_has_prefix() instead of it.
> []
> > diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c
> []
> > @@ -11,10 +11,10 @@
> >
> > int _braille_console_setup(char **str, char **brl_options)
> > {
> > - if (!strncmp(*str, "brl,", 4)) {
> > + if (str_has_prefix(*str, "brl,")) {
> > *brl_options = "";
> > *str += 4;
> > - } else if (!strncmp(*str, "brl=", 4)) {
> > + } else if (str_has_prefix(*str, "brl=")) {
> > *brl_options = *str + 4;
>
> Better to get rid of the += 4 uses too by storing the result
> of str_has_prefix and using that as the addend.
>
> Perhaps
> size_t len;
>
> if ((len = str_has_prefix(*str, "brl,"))) {
> *brl_options = "";
> *str += len;
> } else if ((len = str_has_prefix(*str, "brl="))) {
> etc...
>

I find that checkpatch.pl forbids assignment in if condition.
So this seems to be infeasible...

> > *str = strchr(*brl_options, ',');
> > if (!*str) {
> > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> []
> > @@ -121,13 +121,13 @@ static int __control_devkmsg(char *str)
> > if (!str)
> > return -EINVAL;
> >
> > - if (!strncmp(str, "on", 2)) {
> > + if (str_has_prefix(str, "on")) {
> > devkmsg_log = DEVKMSG_LOG_MASK_ON;
> > return 2;
> > - } else if (!strncmp(str, "off", 3)) {
> > + } else if (str_has_prefix(str, "off")) {
> > devkmsg_log = DEVKMSG_LOG_MASK_OFF;
> > return 3;
> > - } else if (!strncmp(str, "ratelimit", 9)) {
> > + } else if (str_has_prefix(str, "ratelimit")) {
> > devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
> > return 9;
> > }
>
> here too.
>
>

2019-08-01 18:15:17

by Steven Rostedt

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Subject: Re: [PATCH 08/12] printk: Replace strncmp with str_has_prefix

On Thu, 01 Aug 2019 09:19:04 -0700
Joe Perches <[email protected]> wrote:

> > I find that checkpatch.pl forbids assignment in if condition.
> > So this seems to be infeasible...
>
> checkpatch is a stupid script and doesn't forbid
> anything. It's just a suggestion guide.
>
> Ignore checkpatch when you know better.

And this is coming from the checkpatch.pl maintainer ;-)

-- Steve

2019-08-01 18:38:46

by Joe Perches

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Subject: Re: [PATCH 08/12] printk: Replace strncmp with str_has_prefix

On Thu, 2019-08-01 at 23:23 +0800, Chuhong Yuan wrote:
> Joe Perches <[email protected]> 于2019年7月30日周二上午8:16写道：
> > On Mon, 2019-07-29 at 23:15 +0800, Chuhong Yuan wrote:
> > > strncmp(str, const, len) is error-prone.
> > > We had better use newly introduced
> > > str_has_prefix() instead of it.
> > []
> > > diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c
> > []
> > > @@ -11,10 +11,10 @@
> > >
> > > int _braille_console_setup(char **str, char **brl_options)
> > > {
> > > - if (!strncmp(*str, "brl,", 4)) {
> > > + if (str_has_prefix(*str, "brl,")) {
> > > *brl_options = "";
> > > *str += 4;
> > > - } else if (!strncmp(*str, "brl=", 4)) {
> > > + } else if (str_has_prefix(*str, "brl=")) {
> > > *brl_options = *str + 4;
> >
> > Better to get rid of the += 4 uses too by storing the result
> > of str_has_prefix and using that as the addend.
> >
> > Perhaps
> > size_t len;
> >
> > if ((len = str_has_prefix(*str, "brl,"))) {
> > *brl_options = "";
> > *str += len;
> > } else if ((len = str_has_prefix(*str, "brl="))) {
> > etc...
> >
>
> I find that checkpatch.pl forbids assignment in if condition.
> So this seems to be infeasible...

So the code could be rewritten like below:
(though it's trivial as-is)
---
kernel/printk/braille.c | 30 ++++++++++++++++++++----------
1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c
index 1d21ebacfdb8..46dd9fcc7525 100644
--- a/kernel/printk/braille.c
+++ b/kernel/printk/braille.c
@@ -11,19 +11,29 @@

int _braille_console_setup(char **str, char **brl_options)
{
- if (!strncmp(*str, "brl,", 4)) {
+ size_t len;
+
+ len = str_has_prefix(*str, "brl,");
+ if (len) {
*brl_options = "";
- *str += 4;
- } else if (!strncmp(*str, "brl=", 4)) {
- *brl_options = *str + 4;
- *str = strchr(*brl_options, ',');
- if (!*str) {
- pr_err("need port name after brl=\n");
- return -EINVAL;
- }
- *((*str)++) = 0;
+ *str += len;
+ return 0;
+ }
+
+ len = str_has_prefix(*str, "brl=");
+ if (!len)
+ return 0;
+
+ *brl_options = *str + len;
+
+ *str = strchr(*brl_options, ',');
+ if (!*str) {
+ pr_err("need port name after brl=\n");
+ return -EINVAL;
}

+ *((*str)++) = 0;
+
return 0;
}

2019-08-01 22:22:07

by Joe Perches

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