Re: [Qemu-trivial] [Qemu-devel] [PATCH 4/3] checkpatch: Enforce proper do/while (0) style

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> On 11/30/2017 08:01 AM, Eric Blake wrote:
>> while (0) is only idiomatic in a macro definition, where the caller
>> will be supplying the trailing ';'.  Warn if the macro has a duplicate.
>>
>> Signed-off-by: Eric Blake <address@hidden>
>> ---
>>   scripts/checkpatch.pl | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
>> index 34df753571..acb66bff34 100755
>> --- a/scripts/checkpatch.pl
>> +++ b/scripts/checkpatch.pl
>> @@ -1622,6 +1622,11 @@ sub process {
>>                      }
>>              }
>>
>> +# 'while (0);' is odd; only macros should use while (0), without trailing ;
>> +            if ($line =~ /while\s*\(0\);/) {
>
> Should this also check for uses of 'while (false);' ?

Do we think it's likely to occur?

> Interestingly enough, we have an instance of 'do/while (false);' in
> tests/vhost-user-bridge.c that is NOT in a macro, but is used for the
> convenience of being able to 'break;' out early rather than using a
> goto.  Similarly for chardev/char-serial.c using 'while (0);' outside
> of a macro.

That "cure" merely adds gratuitous cleverness to the "disease".

>              Those may be worth rewriting to use goto as separate
> patches if we want to restrict ALL use of 'while \((0|false)\);'

I'd support that.