Re: [bug-gawk] two bugs in gawk 4.0.0 with FPAT and pty

[Aharon Robbins]

Hi.  Thanks for the bug reports.  I have committed fixes for
both these issues to the gawk-4.0-stable branch in the git repo
for gawk on savannah.gnu.org.

> Date: Wed, 3 Aug 2011 17:58:02 -0700 (PDT)
> From: "T. X. G." <address@hidden>
> To: "address@hidden" <address@hidden>
> Subject: [bug-gawk] two bugs in gawk 4.0.0 with FPAT and pty
>
> $ gawk --version
> GNU Awk 4.0.0
> Copyright (C) 1989, 1991-2011 Free Software Foundation.
>
> # bug due to trying to make field splitting more efficient by not parse all 
> fields 
> $ echo a,b,,c |gawk '{for(i=1;i<=4;++i)print i, $i}' FPAT='[^,]*'
> 1 a
> 2 
> 3 b
> 4 
>
> # work around
> $ echo a,b,,c |gawk '{NF;for(i=1;i<=4;++i)print i, $i}' FPAT='[^,]*'
> 1 a
> 2 b
> 3 
> 4 c
>
> This bug, as you commented in function fpat_parse_field, is subtle. The
> null matches of previous call should be remembered across calls. You could
> make the auto variable non_empty static, but then any calls to patsplit
> between references of fields will cause it to be wrong. I guess you can
> either forgo the field splitting optimization by always parse all field
> in the case of FPAT or make a separate function for splitting $0 only
> (or pass an extra arg to it?) I am sure you will find the best fix.
>
>
> The next bug is with pty:
>
> $ gawk 'BEGIN{
> c = "echo 123 > /dev/tty; read x < /dev/tty; echo \"x is $x\""
> PROCINFO[c, "pty"] = 1
> c |& getline;print
> print "abc" |& c
> c |& getline;print
> }'
> 123
> ^C
>
> Adding a call to setsid() in the function two_way_open right after fork
> in the child process seems to fix it.
> 
> One request for feature:
> Currently the format for mktime is not configurable. Could you please
> make it configurable just like strftime through PROCINFO["mktime"]? In
> fact I have already done it myself. But I don't think you would like my
> style. It should be pretty simple for you to implement.

I don't see a big reason for this.  The format is the obvious one, and
making it configurable is just lots more code to write, test, and document,
for a feature that would probably get very little use.  (Yours is the
first request for such a feature since mktime was added to gawk 15.5 years
ago.)

> Thank you, Arnold. Again as I have said before, I enjoy your writings
> and appreciate your contributions to the FSF.
> W. G.

You're quite welcome.  Thank you for the kind words.

Arnold