Re: Crash after a call to pg_backup_start() - Mailing list pgsql-hackers

At Sat, 22 Oct 2022 09:56:06 +0200, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote in 
> On 2022-Oct-21, Michael Paquier wrote:
> 
> > On Fri, Oct 21, 2022 at 05:53:25PM +0800, Richard Guo wrote:
> 
> > >     /* These conditions can not be both true */
> > 
> > If you do that, it would be a bit easier to read as of the following
> > assertion instead?  Like:
> > Assert(!during_backup_start ||
> >        sessionBackupState == SESSION_BACKUP_NONE);
> 
> My intention here was that the Assert should be inside the block, that
> is, we already know that at least one is true, and we want to make sure
> that they are not *both* true.
> 
> AFAICT the attached patch also fixes the bug without making the assert
> weaker.

I'm fine with either of them, but..

The reason for that works the same way is that the if() block excludes
the case of (!during_backup_start && S_B_RUNNING)<*1>. In other words
the strictness is a kind of illusion [*a]. Actually the assertion does
not detect the case <*1>.  In this regard, moving the current
assertion into the if() block might be confusing.

regards,

<*1>: It's evidently superfluous but "strictness" and "illusion" share
 the exactly the same pronounciation in Japanese "Ghen-Ka-Ku".

-- 
Kyotaro Horiguchi
NTT Open Source Software Center