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Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test

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  Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test Viresh Kumar <viresh.kumar@linaro.org> - 2015-08-27 04:20 +0200
    Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL"  test Joe Perches <joe@perches.com> - 2015-08-27 05:10 +0200
      Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL"  test Nicolas Morey Chaisemartin <nmorey@kalray.eu> - 2015-08-27 09:20 +0200
        Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL"  test Joe Perches <joe@perches.com> - 2015-08-27 09:30 +0200
          [PATCH] checkpatch: add constant comparison on left side test Joe Perches <joe@perches.com> - 2015-08-27 19:40 +0200

#1214287 — Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test

On Fri, Nov 14, 2014 at 12:27 AM, Joe Perches <joe@perches.com> wrote:
> It seems there are more and more uses of "if (!ptr)"
> in preference to "if (ptr == NULL)" so add a --strict
> test to emit a message when using the latter form.
>
> This also finds (ptr != NULL).
>
> Fix it too if desired.
>
> Signed-off-by: Joe Perches <joe@perches.com>
> ---
> Seeing no objections, so submitting it.
>
>  scripts/checkpatch.pl | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 24d6702..d4e08bc 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -4490,6 +4490,20 @@ sub process {
>                              "Possible precedence defect with mask then right shift - may need parentheses\n" . $herecurr);
>                 }
>
> +# check for pointer comparisons to NULL
> +               if ($^V && $^V ge 5.10.0) {
> +                       while ($line =~ /\b$LvalOrFunc\s*(==|\!=)\s*NULL\b/g) {
> +                               my $val = $1;
> +                               my $equal = "!";
> +                               $equal = "" if ($4 eq "!=");
> +                               if (CHK("COMPARISON_TO_NULL",
> +                                       "Comparison to NULL could be written \"${equal}${val}\"\n" . $herecurr) &&
> +                                           $fix) {
> +                                       $fixed[$fixlinenr] =~ s/\b\Q$val\E\s*(?:==|\!=)\s*NULL\b/$equal$val/;
> +                               }
> +                       }
> +               }
> +

Hi Joe,

Sorry for picking a relatively old thread.

Few colleagues asked me why isn't checkpatch warning for (NULL == ptr)
or (NULL != ptr) checks, as it warns for (ptr == NULL) and (ptr != NULL).

Did you miss it? or was it intentional ?

--
viresh
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#1214298 — Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test

On Thu, 2015-08-27 at 07:49 +0530, Viresh Kumar wrote:
> Few colleagues asked me why isn't checkpatch warning for (NULL == ptr)
> or (NULL != ptr) checks, as it warns for (ptr == NULL) and (ptr != NULL).
> 
> Did you miss it? or was it intentional ?

I didn't miss it.

NULL == foo is relatively unusual and not really worth the
bother.

And because most likely, "CONST test variable" checks like
	NULL != foo
and
	0 < bar

should probably be a separate test.

Something like:
---
 scripts/checkpatch.pl | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index e14dcdb..457ddef 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4231,6 +4231,29 @@ sub process {
 			}
 		}
 
+# comparisons with a constant on the left
+		if ($^V && $^V ge 5.10.0 &&
+		    $line =~ /\b($Constant|[A-Z_]+)\s*($Compare)\s*($LvalOrFunc)/) {
+			my $const = $1;
+			my $comp = $2;
+			my $to = $3;
+			my $newcomp = $comp;
+			if (WARN("CONSTANT_COMPARISON",
+				 "Comparisons should place the constant on the right side of the test\n" . $herecurr) &&
+			    $fix) {
+				if ($comp eq "<") {
+					$newcomp = ">=";
+				} elsif ($comp eq "<=") {
+					$newcomp = ">";
+				} elsif ($comp eq ">") {
+					$newcomp = "<=";
+				} elsif ($comp eq ">=") {
+					$newcomp = "<";
+				}
+				$fixed[$fixlinenr] =~ s/\(\s*\Q$const\E\s*$Compare\s*\Q$to\E\s*\)/($to $newcomp $const)/;
+			}
+		}
+
 # Return of what appears to be an errno should normally be negative
 		if ($sline =~ /\breturn(?:\s*\(+\s*|\s+)(E[A-Z]+)(?:\s*\)+\s*|\s*)[;:,]/) {
 			my $name = $1;


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#1214361 — Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test

----- Original Message -----
> From: "Joe Perches" <joe@perches.com>
> To: "Viresh Kumar" <viresh.kumar@linaro.org>
> Cc: "Andrew Morton" <akpm@linux-foundation.org>, "Dan Carpenter" <dan.carpenter@oracle.com>, "Greg KH"
> <gregkh@linuxfoundation.org>, "LKML" <linux-kernel@vger.kernel.org>, "Mike Holmes" <mike.holmes@linaro.org>,
> nmorey@kalray.eu
> Sent: Thursday, 27 August, 2015 5:05:37 AM
> Subject: Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test
> 
> On Thu, 2015-08-27 at 07:49 +0530, Viresh Kumar wrote:
> > Few colleagues asked me why isn't checkpatch warning for (NULL == ptr)
> > or (NULL != ptr) checks, as it warns for (ptr == NULL) and (ptr != NULL).
> > 
> > Did you miss it? or was it intentional ?
> 
> I didn't miss it.
> 
> NULL == foo is relatively unusual and not really worth the
> bother.
> 
> And because most likely, "CONST test variable" checks like
> 	NULL != foo
> and
> 	0 < bar
> 
> should probably be a separate test.
> 
> Something like:
> ---
>  scripts/checkpatch.pl | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index e14dcdb..457ddef 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -4231,6 +4231,29 @@ sub process {
>  			}
>  		}
>  
> +# comparisons with a constant on the left
> +		if ($^V && $^V ge 5.10.0 &&
> +		    $line =~ /\b($Constant|[A-Z_]+)\s*($Compare)\s*($LvalOrFunc)/) {
> +			my $const = $1;
> +			my $comp = $2;
> +			my $to = $3;
> +			my $newcomp = $comp;
> +			if (WARN("CONSTANT_COMPARISON",
> +				 "Comparisons should place the constant on the right side of the test\n"
> . $herecurr) &&
> +			    $fix) {
> +				if ($comp eq "<") {
> +					$newcomp = ">=";
> +				} elsif ($comp eq "<=") {
> +					$newcomp = ">";
> +				} elsif ($comp eq ">") {
> +					$newcomp = "<=";
> +				} elsif ($comp eq ">=") {
> +					$newcomp = "<";
> +				}

I like the concept but are you sure about this? I think the "=" should be added or removed. If a < b, b > a, not b >= a.

Nicolas
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#1214365 — Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test

On Thu, 2015-08-27 at 09:09 +0200, Nicolas Morey Chaisemartin wrote:
> > From: "Joe Perches" <joe@perches.com>
[]
> > And because most likely, "CONST test variable" checks like
> > 	NULL != foo
> > and
> > 	0 < bar
> > 
> > should probably be a separate test.
[]
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> > +				if ($comp eq "<") {
> > +					$newcomp = ">=";
> > +				} elsif ($comp eq "<=") {
> > +					$newcomp = ">";
> > +				} elsif ($comp eq ">") {
> > +					$newcomp = "<=";
> > +				} elsif ($comp eq ">=") {
> > +					$newcomp = "<";
> > +				}
> 
> I like the concept but are you sure about this?
> I think the "=" should be added or removed. If a < b, b > a, not b >= a.

Right thanks, it's obviously incorrect.


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#1214740 — [PATCH] checkpatch: add constant comparison on left side test

"CONST <comparison> variable" checks like:

        if (NULL != foo)
and
        while (0 < bar(...))

where a constant (or what appears to be a constant
like an upper case identifier) is on the left of a
comparison are generally preferred to be written
using the constant on the right side like:

        if (foo != NULL)
and
        while (bar(...) > 0)

Add a test for this.

Add a --fix option too, but only do it when the code
is immediately surrounded by parentheses to avoid
misfixing things like "(0 < bar() + constant)"

Signed-off-by: Joe Perches <joe@perches.com>
---
 scripts/checkpatch.pl | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index e14dcdb..5fca1da 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4231,6 +4231,35 @@ sub process {
 			}
 		}
 
+# comparisons with a constant or upper case identifier on the left
+#	avoid cases like "foo + BAR < baz"
+#	only fix matches surrounded by parentheses to avoid incorrect
+#	conversions like "FOO < baz() + 5" being "misfixed" to "baz() > FOO + 5"
+		if ($^V && $^V ge 5.10.0 &&
+		    $line =~ /^\+(.*)\b($Constant|[A-Z_][A-Z0-9_]*)\s*($Compare)\s*($LvalOrFunc)/) {
+			my $lead = $1;
+			my $const = $2;
+			my $comp = $3;
+			my $to = $4;
+			my $newcomp = $comp;
+			if ($lead !~ /$Operators\s*$/ &&
+			    $to !~ /^(?:Constant|[A-Z_][A-Z0-9_]*)$/ &&
+			    WARN("CONSTANT_COMPARISON",
+				 "Comparisons should place the constant on the right side of the test\n" . $herecurr) &&
+			    $fix) {
+				if ($comp eq "<") {
+					$newcomp = ">";
+				} elsif ($comp eq "<=") {
+					$newcomp = ">=";
+				} elsif ($comp eq ">") {
+					$newcomp = "<";
+				} elsif ($comp eq ">=") {
+					$newcomp = "<=";
+				}
+				$fixed[$fixlinenr] =~ s/\(\s*\Q$const\E\s*$Compare\s*\Q$to\E\s*\)/($to $newcomp $const)/;
+			}
+		}
+
 # Return of what appears to be an errno should normally be negative
 		if ($sline =~ /\breturn(?:\s*\(+\s*|\s+)(E[A-Z]+)(?:\s*\)+\s*|\s*)[;:,]/) {
 			my $name = $1;


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