Re: [PATCH] udevd: Avoid implicit memset in match_attr()

[Alan Jenkins <alan-jenkins@tuffmail.co.uk>]

Kay Sievers wrote:
> On Sat, Oct 25, 2008 at 16:51, Alan Jenkins <alan-jenkins@tuffmail.co.uk> wrote:
>   
>> C initializers include an implicit "others => 0" (Ada syntax).
>> Initializing a char array to "" is equivalent to a memset()
>> call - which is exactly what it gets compiled to.
>>
>> Fixing this one callsite reduced memset() _user_ cpu cycles
>> from 2-4% to 0.05% on the EeePC.
>>
>> There are other occurences, but the fix isn't that pretty
>> so I left them alone.
>>
>> Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
>>
>> diff --git a/udev/udev-rules.c b/udev/udev-rules.c
>> index 45806c3..ad2b00f 100644
>> --- a/udev/udev-rules.c
>> +++ b/udev/udev-rules.c
>> @@ -1559,10 +1559,11 @@ static int match_attr(struct udev_rules *rules, struct udev_device *dev, struct
>>        char attr[UTIL_PATH_SIZE];
>>        const char *key_name = &rules->buf[cur->key.attr_off];
>>        const char *key_value = &rules->buf[cur->key.value_off];
>> -       char value[UTIL_NAME_SIZE] = "";
>> +       char value[UTIL_NAME_SIZE];
>>        size_t len;
>>
>>        util_strlcpy(attr, key_name, sizeof(attr));
>> +       util_strlcpy(value, "", sizeof(value));
>>     
>
> Wouldn't value[0] = '\0' be even faster? :)
>   

Heh.  That would probably be clearer as well.  There's no big
difference, use whatever you prefer.