Re: Two noncritical bugs of pg_waldump

Hmm..

At Thu, 27 Jan 2022 10:07:38 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in 
> pg_waldump complains at the end in any case.  I noticed that the LSN
> it shows in the finish message is incorrect.  (I faintly thought that
> I posted about this but I didn't find it..)
> 
> > pg_waldump: fatal: error in WAL record at 0/15073F8: invalid record length at 0/1507470: wanted 24, got 0
> 
> xlogreader found the error at the record begins at 1507470, but
> pg_waldump tells that error happens at 15073F8, which is actually the
> beginning of the last sound record.

It is arguable, but the following is indisputable.

> If I give an empty file to the tool it complains as the follows.
> 
> > pg_waldump: fatal: could not read file "hoge": No such file or directory
> 
> No, the file exists.  The cause is it reads uninitialized errno to
> detect errors from the system call.  read(2) is defined to set errno
> always when it returns -1 and doesn't otherwise. Thus it seems to me
> that it is better to check that the return value is less than zero
> than to clear errno before the call to read().

So I post a patch contains only the indisputable part.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center