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Don't fork the last command in a forked subshell (re: c0c7d0f, f0b0b67) #935

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Don't fork the last command in a forked subshell (re: c0c7d0f, f0b0b67) #935

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5 changes: 1 addition & 4 deletions src/cmd/ksh93/sh/subshell.c
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Original file line number Diff line number Diff line change
Expand Up @@ -679,13 +679,10 @@ Sfio_t *sh_subshell(Shnode_t *t, volatile int flags, int comsub)
sfswap(iop,sfstdout);
sfset(sfstdout,SFIO_READ,0);
sh.fdstatus[1] = IOWRITE;
flags |= sh_state(SH_NOFORK);
}
else if(sp->prev)
{
sp->pipe = sp->prev->pipe;
flags &= ~sh_state(SH_NOFORK);
}
flags |= sh_state(SH_NOFORK);
if(sh.savesig < 0)
{
sh.savesig = 0;
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32 changes: 32 additions & 0 deletions src/cmd/ksh93/tests/basic.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -987,6 +987,15 @@ esac
# ======
# Test exec optimization of last command in script or subshell

(
ulimit -t unlimited 2>/dev/null # fork subshell
print "${.sh.pid:-$("$SHELL" -c 'echo "$PPID"')}" # fallback for pre-93u+m ksh without ${.sh.pid}
"$SHELL" -c 'print "$$"'
) >out
pid1= pid2=
{ read pid1 && read pid2; } <out && let "pid1 == pid2" \
|| err_exit "last command in forked subshell not exec-optimized ($pid1 != $pid2)"

got=$(
ulimit -t unlimited 2>/dev/null # fork subshell
print "${.sh.pid:-$("$SHELL" -c 'echo "$PPID"')}" # fallback for pre-93u+m ksh without ${.sh.pid}
Expand All @@ -996,6 +1005,29 @@ pid1= pid2=
{ read pid1 && read pid2; } <<<$got && let "pid1 == pid2" \
|| err_exit "last command in forked comsub not exec-optimized ($pid1 != $pid2)"

# https://github.com/ksh93/ksh/issues/507
mkdir "$tmp/subshell-optimize"
cat <<'EOF1' >"$tmp/subshell-optimize/A"
cat <<'EOF2' >B
( echo B1 ) | cat
( echo B2 ) | cat
EOF2

cat <<'EOF2' >C
( echo C1 ) | cat
( echo C2 ) | cat
EOF2

(
. ./B
. ./C
) | cat
EOF1
exp=$'B1\nB2\nC1\nC2'
got=$(cd "$tmp/subshell-optimize"; "$SHELL" "$tmp/subshell-optimize/A")
[[ $exp == $got ]] || err_exit "last command exec optimization in virtual subshells is broken" \
"(expected $(printf %q "$exp"), got $(printf %q "$got"))"

cat >script <<\EOF
echo $$
sh -c 'echo $$'
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