Re: [PATCH] checkpatch: Detect '%#' or '%0#' in printf-style format strings

[Philippe Mathieu-Daudé]

On 9/14/20 1:27 PM, Dov Murik wrote:
> On 14/09/2020 9:55, Philippe Mathieu-Daudé wrote:
>> +qemu-perl team
>>
>> On 9/14/20 8:01 AM, Dov Murik wrote:
>>> According to the coding style document, we should use literal '0x'
>>> prefix
>>> instead of printf's '#' flag (which appears as '%#' or '%0#' in the
>>> format
>>> string).  Add a checkpatch rule to enforce that.
>>>
>>> Note that checkpatch already had a similar rule for trace-events files.
>>>
>>> Example usage:
>>>
>>>    $ scripts/checkpatch.pl --file chardev/baum.c
>>>    ...
>>>    ERROR: Don't use '#' flag of printf format ('%#') in format
>>> strings, use '0x' prefix instead
>>>    #366: FILE: chardev/baum.c:366:
>>>    +            DPRINTF("Broken packet %#2x, tossing\n", req); \
>>>    ...
>>>    ERROR: Don't use '#' flag of printf format ('%#') in format
>>> strings, use '0x' prefix instead
>>>    #472: FILE: chardev/baum.c:472:
>>>    +        DPRINTF("unrecognized request %0#2x\n", req);
>>>    ...
>>>
>>> Signed-off-by: Dov Murik <dovmurik@linux.vnet.ibm.com>
>>> ---
>>>   scripts/checkpatch.pl | 12 ++++++++++++
>>>   1 file changed, 12 insertions(+)
>>>
>>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
>>> index bd3faa154c..6ec2a9f6a1 100755
>>> --- a/scripts/checkpatch.pl
>>> +++ b/scripts/checkpatch.pl
>>> @@ -2891,6 +2891,18 @@ sub process {
>>>               }
>>>           }
>>>   +# check for %# or %0# in printf-style format strings
>>> +        while ($line =~ /(?:^|")([X\t]*)(?:"|$)/g) {
>>> +            my $string = substr($rawline, $-[1], $+[1] - $-[1]);
>>> +            $string =~ s/%%/__/g;
>>> +            if ($string =~ /(?<!%)%0?#/) {
>>> +                ERROR("Don't use '#' flag of printf format " .
>>> +                      "('%#') in format strings, use '0x' " .
>>> +                      "prefix instead\n" . $herecurr);
>>> +                last;
>>> +            }
>>> +        }
>>> +
>>>   # QEMU specific tests
>>>           if ($rawline =~ /\b(?:Qemu|QEmu)\b/) {
>>>               ERROR("use QEMU instead of Qemu or QEmu\n" . $herecurr);
>>>
>>
>> Thank you for this patch!
>>
>> What about folding it in the same block?
>>
> 
> That makes sense, except that 'last' statement which will escape the
> loop if one of the bad patterns is found.
> 
> Maybe we can just drop 'last' from both if-then blocks?  We'll get
> multiple alerts if bad patterns are used more than once in the same
> line, which sounds OK to me.

No objection.

> 
> 
>> -- >8 --
>> --- a/scripts/checkpatch.pl
>> +++ b/scripts/checkpatch.pl
>> @@ -2880,15 +2880,22 @@ sub process {
>>                                  $herecurr);
>>                  }
>>
>> -# check for %L{u,d,i} in strings
>> +# format strings checks
>>                  my $string;
>>                  while ($line =~ /(?:^|")([X\t]*)(?:"|$)/g) {
>>                          $string = substr($rawline, $-[1], $+[1] -
>> $-[1]);
>>                          $string =~ s/%%/__/g;
>> +                       # check for %L{u,d,i} in strings
>>                          if ($string =~ /(?<!%)%L[udi]/) {
>>                                  ERROR("\%Ld/%Lu are not-standard C, use
>> %lld/%llu\n" . $herecurr);
>>                                  last;
>>                          }
>> +                       if ($string =~ /(?<!%)%0?#/) {
>> +                               ERROR("Don't use '#' flag of printf
>> format " .
>> +                                     "('%#') in format strings, use
>> '0x' " .
>> +                                     "prefix instead\n" . $herecurr);
>> +                               last;
>> +                       }
>>                  }
>>
>>   # QEMU specific tests
>> ---
>>
>