Re: [Qemu-devel] [PATCH] checkpatch: Don't spuriously warn about /** comment starters

[Eric Blake]

On 1/18/19 7:27 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.

Just wondering if "/\*{1,2}" would also work (it may have to be spelled
"/\*\{1,2}" - I never remember which flavors of regex have which
extensions without rereading docs).  But since your way is tested, I'm
not going to force a respin.

> 
> Reported-by: Thomas Huth <address@hidden>
> Signed-off-by: Peter Maydell <address@hidden>
> ---
> This comment check is unique to QEMU checkpatch so the bug
> doesn't exist in the Linux version.
> ---
>  scripts/checkpatch.pl | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index d10dddf1be4..5f1ec537d21 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -1624,7 +1624,7 @@ sub process {
>  
>               # Block comments use /* on a line of its own
>               if ($rawline !~ address@hidden/\*.*\*/[ \t]*$@ &&       #inline 
> /*...*/
> -                 $rawline =~ address@hidden/\*\*?[ \t]*.+[ \t]*$@) { # /* or 
> /** non-blank
> +                 $rawline =~ address@hidden/\*\*?+[ \t]*.+[ \t]*$@) { # /* 
> or /** non-blank

Hmm - Isn't "[ \t]*.+[ \t]*$" the same as ".+$?"  Perhaps:

address@hidden/\*([^*]|\*.)@

also does the trick in a more legible way (that is, any line that starts
with /* and then contains any additional characters other than a second *)?

Reviewed-by: Eric Blake <address@hidden>

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

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