Re: [Qemu-devel] [PATCH v2] checkpatch: Don't emit spurious warnings about block comments

[Eric Blake <eblake@redhat.com>]

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On 1/18/19 10:50 AM, Peter Maydell wrote:
> In checkpatch we attempt to check for and warn about
> block comments which start with /* or /** followed by a
> non-blank. Unfortunately a bug in the regex meant that
> we would incorrectly warn about comments starting with
> "/**" with no following text:
> 
>   git show 9813dc6ac3954d58ba16b3920556f106f97e1c67|./scripts/checkpatch.pl -
>   WARNING: Block comments use a leading /* on a separate line
>   #34: FILE: tests/libqtest.h:233:
>   +/**
> 
> The sequence "/\*\*?" was intended to match either "/*" or "/**",
> but Perl's semantics for '?' allow it to backtrack and try the
> "matches 0 chars" option if the "matches 1 char" choice leads to
> a failure of the rest of the regex to match.  Switch to "/\*\*?+"
> which uses what perlre(1) calls the "possessive" quantifier form:
> this means that if it matches the "/**" string it will not later
> backtrack to matching just the "/*" prefix.
> 
> The other end of the regex is also wrong: it is attempting
> to check for "/* or /** followed by something that isn't
> just whitespace", but [ \t]*.+[ \t]* will match on pure
> whitespace. This is less significant but means that a line
> with just a comment-starter followed by trailing whitespace
> will generate an incorrect warning about block comment style
> as well as the correct error about trailing whitespace which
> a different checkpatch test emits.
> 

Fixes: 8c06fbdf36bf4d4d486116200248730887a4d7d6

> Reported-by: Thomas Huth <thuth@redhat.com>
> Reported-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---

>  		# Block comments use /* on a line of its own
>  		if ($rawline !~ m@^\+.*/\*.*\*/[ \t]*$@ &&	#inline /*...*/
> -		    $rawline =~ m@^\+.*/\*\*?[ \t]*.+[ \t]*$@) { # /* or /** non-blank
> +		    $rawline =~ m@^\+.*/\*\*?+[ \t]*[^ \t]@) { # /* or /** non-blank

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

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org


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