Thread: What behavior is in this loop?

Hi,

I found interesting "for" and "while" loop in WaitForWALToBecomeAvailable() in
xlog.c. Can you tell me this behavior?

for (;;)
{
~
} while (StanbyMode)

I confirmed this code is no problem in gcc compiler:)

Regards,
--
Mitsumasa KONDO
NTT Open Source Software Center

On 02/27/2014 12:38 PM, KONDO Mitsumasa wrote:
> I found interesting "for" and "while" loop in WaitForWALToBecomeAvailable() in
> xlog.c. Can you tell me this behavior?
>
> for (;;)
> {
> ~
> } while (StanbyMode)
>
> I confirmed this code is no problem in gcc compiler:)

Oh wow :-). That's clearly a thinko, although harmless in this case. 
Looking at the git history, I made that mistake in commit abf5c5c9a. 
Before that, there was no "while".

That's easier to understand with some extra formatting. That's two 
loops, like this:

/* loop 1 */
for (;;)
{  ...
}

/* loop2 */
while(StandbyMode);

The second loop is obviously completely pointless. Thankfully, the there 
are no "breaks" inside the first loop (the ones within the 
switch-statements don't count), so the endless while-loop is never reached.

I'll go fix that... Thanks for the report!

- Heikki

(2014/02/27 20:19), Heikki Linnakangas wrote:
> On 02/27/2014 12:38 PM, KONDO Mitsumasa wrote:
>> I found interesting "for" and "while" loop in WaitForWALToBecomeAvailable() in
>> xlog.c. Can you tell me this behavior?
>>
>> for (;;)
>> {
>> ~
>> } while (StanbyMode)
>>
>> I confirmed this code is no problem in gcc compiler:)
>
> Oh wow :-). That's clearly a thinko, although harmless in this case. Looking at
> the git history, I made that mistake in commit abf5c5c9a. Before that, there was
> no "while".
>
> That's easier to understand with some extra formatting. That's two loops, like this:
>
> /* loop 1 */
> for (;;)
> {
>    ...
> }
>
> /* loop2 */
> while(StandbyMode);
>
> The second loop is obviously completely pointless. Thankfully, the there are no
> "breaks" inside the first loop (the ones within the switch-statements don't
> count), so the endless while-loop is never reached.
Yeah, StandbyMode flag doesn't change in this loop.

> I'll go fix that... Thanks for the report!
Thanks for your kind!

By the way, I found cannot promote problem in PG9.3.3 in standby mode with 
archive revovery and crash recovery situations. I analyze this problem and fix it 
now. Please take care of then!

Regards,
--
Mitsumasa KONDO
NTT Open Source Software Center