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

From: T. X. G.
Subject: [bug-gawk] two bugs in gawk 4.0.0 with FPAT and pty
Date: Wed, 3 Aug 2011 17:58:02 -0700 (PDT)

$ 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 
$ echo a,b,,c |gawk '{for(i=1;i<=4;++i)print i, $i}' FPAT='[^,]*'
1 a
3 b

# work around
$ echo a,b,,c |gawk '{NF;for(i=1;i<=4;++i)print i, $i}' FPAT='[^,]*'
1 a
2 b
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

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.

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

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