[PATCH] checkpatch: Improve TYPECAST_INT_CONSTANT test message

[PATCH] checkpatch: Improve TYPECAST_INT_CONSTANT test message

[Joe Perches]

Improve the TYPECAST_INT_CONSTANT test by showing the suggested
conversion for various type of uses like (unsigned int)1 to 1U.

Signed-off-by: Joe Perches <joe@perches.com>
---

Douglas Gilbert sent me a private email (and in that email said he
'loves to hate checkpatch' ;) complaining that checkpatch warned on the
use of the cast of '(unsigned int)1' so make it more obvious why the
message is emitted by always showing the suggested conversion.

 scripts/checkpatch.pl | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 016115a62a9f..4f8494527139 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6527,18 +6527,18 @@ sub process {
 		if ($line =~ /(\(\s*$C90_int_types\s*\)\s*)($Constant)\b/) {
 			my $cast = $1;
 			my $const = $2;
+			my $suffix = "";
+			my $newconst = $const;
+			$newconst =~ s/${Int_type}$//;
+			$suffix .= 'U' if ($cast =~ /\bunsigned\b/);
+			if ($cast =~ /\blong\s+long\b/) {
+			    $suffix .= 'LL';
+			} elsif ($cast =~ /\blong\b/) {
+			    $suffix .= 'L';
+			}
 			if (WARN("TYPECAST_INT_CONSTANT",
-				 "Unnecessary typecast of c90 int constant\n" . $herecurr) &&
+				 "Unnecessary typecast of c90 int constant - '$cast$const' could be '$const$suffix'\n" . $herecurr) &&
 			    $fix) {
-				my $suffix = "";
-				my $newconst = $const;
-				$newconst =~ s/${Int_type}$//;
-				$suffix .= 'U' if ($cast =~ /\bunsigned\b/);
-				if ($cast =~ /\blong\s+long\b/) {
-					$suffix .= 'LL';
-				} elsif ($cast =~ /\blong\b/) {
-					$suffix .= 'L';
-				}
 				$fixed[$fixlinenr] =~ s/\Q$cast\E$const\b/$newconst$suffix/;
 			}
 		}

Re: [PATCH] checkpatch: Improve TYPECAST_INT_CONSTANT test message

[Douglas Gilbert]

On 2021-01-18 12:19 p.m., Joe Perches wrote:
> Improve the TYPECAST_INT_CONSTANT test by showing the suggested
> conversion for various type of uses like (unsigned int)1 to 1U.

The questionable code snippet was:
         unsigned int nent, nalloc;

         ....
         if (check_add_overflow(nent, (unsigned int)1, &nalloc))

where the check_add_overflow() macro [include/linux/overflow.h]
uses typeid to check its first and second arguments have the
same type. So it is likely others could meet this issue.

Doug Gilbert


> Signed-off-by: Joe Perches <joe@perches.com>
> ---
> 
> Douglas Gilbert sent me a private email (and in that email said he
> 'loves to hate checkpatch' ;) complaining that checkpatch warned on the
> use of the cast of '(unsigned int)1' so make it more obvious why the
> message is emitted by always showing the suggested conversion.
> 
>   scripts/checkpatch.pl | 20 ++++++++++----------
>   1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 016115a62a9f..4f8494527139 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6527,18 +6527,18 @@ sub process {
>   		if ($line =~ /(\(\s*$C90_int_types\s*\)\s*)($Constant)\b/) {
>   			my $cast = $1;
>   			my $const = $2;
> +			my $suffix = "";
> +			my $newconst = $const;
> +			$newconst =~ s/${Int_type}$//;
> +			$suffix .= 'U' if ($cast =~ /\bunsigned\b/);
> +			if ($cast =~ /\blong\s+long\b/) {
> +			    $suffix .= 'LL';
> +			} elsif ($cast =~ /\blong\b/) {
> +			    $suffix .= 'L';
> +			}
>   			if (WARN("TYPECAST_INT_CONSTANT",
> -				 "Unnecessary typecast of c90 int constant\n" . $herecurr) &&
> +				 "Unnecessary typecast of c90 int constant - '$cast$const' could be '$const$suffix'\n" . $herecurr) &&
>   			    $fix) {
> -				my $suffix = "";
> -				my $newconst = $const;
> -				$newconst =~ s/${Int_type}$//;
> -				$suffix .= 'U' if ($cast =~ /\bunsigned\b/);
> -				if ($cast =~ /\blong\s+long\b/) {
> -					$suffix .= 'LL';
> -				} elsif ($cast =~ /\blong\b/) {
> -					$suffix .= 'L';
> -				}
>   				$fixed[$fixlinenr] =~ s/\Q$cast\E$const\b/$newconst$suffix/;
>   			}
>   		}
> 
>