Date: Tue, 7 Sep 1999 21:03:43 +0800 (CST) From: Scott Hazen Mueller <scott@zorch.sf-bay.org> To: FreeBSD-gnats-submit@freebsd.org Cc: scott@zorch.sf-bay.org Subject: bin/13615: awk bug Message-ID: <199909071303.VAA12164@zorba.sf-bay.org>
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>Number: 13615
>Category: bin
>Synopsis: awk corrupts the memory arena when OFMT is not %.6g
>Confidential: no
>Severity: critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Sep 7 06:10:01 PDT 1999
>Closed-Date:
>Last-Modified:
>Originator: Scott Hazen Mueller
>Release: FreeBSD 3.2-RELEASE i386
>Organization:
none
>Environment:
The code originates in C News, however all C News dependencies have been
removed from the supplied test case.
>Description:
When the supplied script is run against the supplied test data with
OFMT unset or set to the default %.6g, the script completes normally.
If OFMT is set to a value other than %.6g (values tested from %.7g to
%.12g), the script generates numerous
awk in free(): warning: chunk is already free.
warnings. Additionally, variable values change unexpectedly in apparent
response to assignment of other variables.
This is the output of a "normal" run:
123123123123 1e+11
now0 123123123123 123123123123 1e+11 <--- 1st checkpoint
now1 123123123123 0 1e+11
now2 123123123123 0 1e+11
123123123123 456456456456 1e+11
now0 456456456456 456456456456 1e+11 <--- 2nd checkpoint
now1 456456456456 0 1e+11
now2 456456456456 0 1e+11
456456456456 789789789789 1e+11
now0 789789789789 789789789789 1e+11 <--- 3rd checkpoint
now1 789789789789 0 1e+11
now2 789789789789 0 1e+11
This is the output when OFMT is %.7g:
1.231231e+11 1e+11
awk in free(): warning: chunk is already free.
now0 123123123123 1e+11 1e+11 <--- 1st checkpoint
awk in free(): warning: chunk is already free.
now1 123123123123 1e+11 1e+11
now2 123123123123 1e+11 1e+11
awk in free(): warning: chunk is already free.
123123123123 4.564564e+11 4.564564e+11
now0 456456456456 456456456456 456456456456 <--- 2nd checkpoint
awk in free(): warning: chunk is already free.
awk in free(): warning: chunk is already free.
now1 0 0 0 <--- error
awk in free(): warning: chunk is already free.
awk in free(): warning: chunk is already free.
now2 0 0 0
awk in free(): warning: chunk is already free.
awk in free(): warning: chunk is already free.
7.897898e+11 7.897898e+11 7.897898e+11 <--- 3rd checkpoint awk in free(): warning: chunk is already free.
awk in free(): warning: chunk is already free.
now1 6.653991e-316 6.653991e-316 6.653991e-316 <--- error
awk in free(): warning: chunk is already free.
awk in free(): warning: chunk is already free.
now2 9.999994e+10 9.999994e+10 9.999994e+10
Note that in the second output set, the variable values went to '0 0 0'
between the 2nd and 3rd checkpoint, and went to 6.65e-316 after the 3rd
checkpoint. These output lines are indicated with 'error'.
>How-To-Repeat:
awk script:
BEGIN {
OFMT = "%.7g"
#OFMT = "%.6g"
big = 99999999999
lowest = big
small = 0
highest = small
dir = ""
}
{
if ($1 < lowest)
lowest = $1
if ($1 > highest)
highest = $1
print dir, highest, lowest
dir = $0
print "now0 ", dir, highest, lowest
highest = small
print "now1 ", dir, highest, lowest
lowest = big
print "now2 ", dir, highest, lowest
}
input file:
123123123123
456456456456
789789789789
Execute awk -f script <input
To see the normal case, uncomment 'OFMT="%.6g"'.
Note on the script - the seemingly meaningless tests and assignments
are necessary to reproduce the error condition. This is the simplest
script I could generate that reproduced the failure.
>Fix:
Setting OFMT to %.6g seems to cause normal behavior, at the loss of
flexibility in formatting the output.
>Release-Note:
>Audit-Trail:
>Unformatted:
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