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ash: regressions in process substitution

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Stacy Harper reports that this script:

   test() { . /tmp/bb_test; }
   echo "export TEST=foo" >/tmp/bb_test
   test 2>/dev/null
   echo "$TEST"

correctly prints 'foo' in BusyBox 1.33 but hangs in 1.34.

Bisection suggested the problem was caused by commit a1b0d3856 (ash: add
process substitution in bash-compatibility mode).  Removing the call to
unwindredir() in cmdloop() introduced in that commit makes the script
work again.

Additionally, these examples of process substitution:

   while true; do cat <(echo hi); done
   f() { while true; do cat <(echo hi); done }
   f

result in running out of file descriptors.  This is a regression from
v5 of the process substitution patch caused by changes to evalcommand()
not being transferred to v6.

function                                             old     new   delta
static.pushredir                                       -      99     +99
evalcommand                                         1729    1750     +21
exitreset                                             69      86     +17
cmdloop                                              372     365      -7
unwindredir                                           28       -     -28
pushredir                                            112       -    -112
------------------------------------------------------------------------------
(add/remove: 1/2 grow/shrink: 2/1 up/down: 137/-147)          Total: -10 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Ron Yorston 2021-08-30 20:31:42 +01:00 committed by Denys Vlasenko
parent f02691939e
commit 4a36ef11ac
1 changed files with 7 additions and 3 deletions
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10
shell/ash.c
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@ -10278,6 +10278,9 @@ evalcommand(union node *cmd, int flags)
/* First expand the arguments. */ /* First expand the arguments. */
TRACE(("evalcommand(0x%lx, %d) called\n", (long)cmd, flags)); TRACE(("evalcommand(0x%lx, %d) called\n", (long)cmd, flags));
#if BASH_PROCESS_SUBST
redir_stop = redirlist;
#endif
file_stop = g_parsefile; file_stop = g_parsefile;
back_exitstatus = 0; back_exitstatus = 0;
@ -10356,7 +10359,11 @@ evalcommand(union node *cmd, int flags)
lastarg = nargv[-1]; lastarg = nargv[-1];
expredir(cmd->ncmd.redirect); expredir(cmd->ncmd.redirect);
#if !BASH_PROCESS_SUBST
redir_stop = pushredir(cmd->ncmd.redirect); redir_stop = pushredir(cmd->ncmd.redirect);
#else
pushredir(cmd->ncmd.redirect);
#endif
preverrout_fd = 2; preverrout_fd = 2;
if (BASH_XTRACEFD && xflag) { if (BASH_XTRACEFD && xflag) {
/* NB: bash closes fd == $BASH_XTRACEFD when it is changed. /* NB: bash closes fd == $BASH_XTRACEFD when it is changed.
@ -13476,9 +13483,6 @@ cmdloop(int top)
#if JOBS #if JOBS
if (doing_jobctl) if (doing_jobctl)
showjobs(SHOW_CHANGED|SHOW_STDERR); showjobs(SHOW_CHANGED|SHOW_STDERR);
#endif
#if BASH_PROCESS_SUBST
unwindredir(NULL);
#endif #endif
inter = 0; inter = 0;
if (iflag && top) { if (iflag && top) {