Re: [libvirt] [PATCH] conf: check rombar against VIR_DOMAIN_TRISTATE_SWITCH_ABSENT
On 08/07/2017 05:30 PM, Pavel Hrdina wrote:
On Mon, Aug 07, 2017 at 05:06:49PM +0200, Michal Privoznik wrote:
> On 08/07/2017 04:56 PM, Ján Tomko wrote:
>> Make the comparison explicit.
>> ---
>> src/conf/domain_conf.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
>> index 3cdb5e348..b5ce2ecd9 100644
>> --- a/src/conf/domain_conf.c
>> +++ b/src/conf/domain_conf.c
>> @@ -5359,10 +5359,10 @@ virDomainDeviceInfoFormat(virBufferPtr buf,
>> }
>>
>> if ((flags & VIR_DOMAIN_DEF_FORMAT_ALLOW_ROM) &&
>> - (info->rombar || info->romfile)) {
>> + (info->rombar != VIR_TRISTATE_SWITCH_ABSENT || info->romfile)) {
>>
>> virBufferAddLit(buf, "<rom");
>> - if (info->rombar) {
>> + if (info->rombar != VIR_TRISTATE_SWITCH_ABSENT) {
>> const char *rombar =
virTristateSwitchTypeToString(info->rombar);
>>
>> if (rombar)
>>
>
> I'm not against this patch, it's just that we set ABSENT explicitly to
> zero value so that we can do shortcuts like this. If we don't want to
> have them, we ought to remove the explicit value assignment.
The shortcut is nice, but I don't like it personally. If the variable
can contain more than two states I'd rather check it explicitly.
So what's the point of assigning _ABSENT zero value then?
That's
why I prefer (int == 0) over (!int).
Well, if this is a part of bigger statement then yes, for instance:
if (x == 0) {
} else if (x == 1) {
} else {
}
(although, sometimes we might prefer switch() for that). But if it's
just a simple check whether a value was set or is equal to some default
(= if the check is interested in distinguishing just two states anyway),
!var works for me too:
if (x)
formatToXML(x)
But sure, var == 0 vs !var is a personal preference. The important part
is my first question. If we dislike these shortcuts (in either of their
form), shouldn't we just drop explicit value assignment in the enum?
Michal