Re: [Qemu-devel] [PATCH v5 04/46] checkpatch: Recognize IEC binary prefix definitions

[Eric Blake <eblake@redhat.com>]

On 06/25/2018 07:41 AM, Philippe Mathieu-Daudé wrote:
> Do not match the IEC binary prefix as camelcase typedefs.
> 
> This fixes:
> 
>      ERROR: "foo * bar" should be "foo *bar"
>      #310: FILE: hw/ppc/ppc440_uc.c:564:
>      +        size = 8 * MiB * sh;
>      total: 1 errors, 0 warnings, 433 lines checked
> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>   scripts/checkpatch.pl | 1 +
>   1 file changed, 1 insertion(+)

Warning - my perl regex-fu is weak; but I'll give this a shot.

> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index e3d8c2cdfc..223681bfd0 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -242,6 +242,7 @@ our $UTF8	= qr{
>   # There are still some false positives, but this catches most
>   # common cases.
>   our $typeTypedefs = qr{(?x:
> +        (?![KMGTPE]iB)                      # IEC binary prefix (do not match)

I had to (re-)read 'perldoc perlretut', but found what I was looking 
for.  You are adding a zero-length negated lookahead assertion that 
anything matching the pattern [KMGTPE]iB is not matched to the rest of 
the regex.

>           [A-Z][A-Z\d_]*[a-z][A-Za-z\d_]*     # camelcase
>           | [A-Z][A-Z\d_]*AIOCB               # all uppercase
>           | [A-Z][A-Z\d_]*CPU                 # all uppercase

and the rest of this regex is picking out any sequence that the code 
should treat as a typedef.  Ergo, with your negative lookahead, we are 
no longer treating the numeric mixed-case constants as typedefs, and the 
rest of the script that warns on formatting issues where a typedef 
appears to be used with a '*' for creating a pointer no longer trigger.

Since that's enough to shut up the false positives you were seeing, then 
it looks right to me.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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