mksh

regression re. fd redirections in COMSUB with TIF

Bug #907224 reported by Thorsten Glaser on 2011-12-21

This bug affects 1 person

Affects		Status	Importance	Assigned to	Milestone
	mksh	Fix Released	Undecided	Unassigned

Bug Description

Original code found in /bin/zgrep on Debian Lenny.

tglase@tglase:~ $ cat reduced-testcase
exec 3>&1
echo = start one
captured=$(
exec 5>&1
(echo one-u; echo 0 >&5) | { tr u x; } >&3
)
echo "= captured<$captured>"

echo

echo = start two
captured=$(
exec 5>&1
(echo two-u; echo 0 >&5) | if :; then tr u x; fi >&3
)
echo "= captured<$captured>"
tglase@tglase:~ $ posh reduced-testcase
= start one
one-x
= captured<0>

= start two
two-x
= captured<0>
tglase@tglase:~ $ mksh reduced-testcase
= start one
one-x
= captured<0>

= start two
= captured<0
two-x>
tglase@tglase:~ $ mksh -o sh reduced-testcase
= start one
one-x
= captured<0>

= start two
= captured<0
two-x>
tglase@tglase:~ $ mksh -o posix reduced-testcase
= start one
one-x
= captured<0>

= start two
= captured<0
two-x>

Tracking down the changes:

tg@blau:~ $ mksh-R39c reduced-testcase
= start one
one-x
= captured<0>

= start two
two-x
= captured<0>
tg@blau:~ $ mksh-R40 reduced-testcase
= start one
one-x
= captured<0>

= start two
= captured<0
two-x>

This may or may not be related to the COMSUB rewrite.

Oh well, actually it is:

1|tg@blau:~ $ mksh-R39c tf
one() {
    exec 3>&1
    captured=$(^J^I^Iexec 5>&1^J^I^I(echo one-u; echo 0 >&5) | { tr u x; } >&3^J^I)
}
two() {
    exec 3>&1
    captured=$(^J^I^Iexec 5>&1^J^I^I(echo two-u; echo 0 >&5) | if :; then tr u x; fi >&3^J^I)
}
tg@blau:~ $ mksh-R40 tf
one() {
        exec 3>&1
        captured=$(exec 5>&1 ; ( echo one-u ; echo 0 >&5 ) | { tr u x ; } >&3 )
}
two() {
        exec 3>&1
        captured=$(exec 5>&1 ; ( echo two-u ; echo 0 >&5 ) | if : ; then tr u x ; fi )
}

This definitively needs tree-dump investigation.

Further reduced:

tg@blau:~ $ mksh-R39c -c 'exec 3>&1; x=$(echo 1; if :; then echo 3; echo >&2 2; fi >&3); echo "<$x>"'
3
2
<1>
tg@blau:~ $ mksh-R40 -c 'exec 3>&1; x=$(echo 1; if :; then echo 3; echo >&2 2; fi >&3); echo "<$x>"'
2
<1
3>