Re: ash backgrounding bug?

[christos%astron.com@localhost (Christos Zoulas)]

In article <20140605131250.GD49530%trav.math.uni-bonn.de@localhost>,
Edgar Fuß  <ef%math.uni-bonn.de@localhost> wrote:
>If I do
>
>#!/bin/sh
>
>daemon() {
>       sleep 5
>}
>
>fork_daemon() {
>       ( cd /; $1 <&- >&- 2>&- & echo $! ) &
>}
>
>daemon_pid=$(fork_daemon daemon)
>echo "daemon pid=$daemon_pid"
>
>with any non-ash POSIX shell I can find, it works as I expect.
>When using ash (or dash), the $() evaluation waits for daemon() to return.
>Is that a bug in ash or does POSIX allow such behaviour?

Looks like a bug to me. Note that this is not due to vfork() I think because
the following patch and invoking sh -F does the same. Send-pr?

christos

Index: eval.c
===================================================================
RCS file: /cvsroot/src/bin/sh/eval.c,v
retrieving revision 1.109
diff -u -u -r1.109 eval.c
--- eval.c      31 May 2014 14:42:18 -0000      1.109
+++ eval.c      5 Jun 2014 15:43:29 -0000
@@ -860,7 +860,7 @@
                 * child's address space is actually shared with the parent as
                 * we rely on this.
                 */
-               if (cmdentry.cmdtype == CMDNORMAL) {
+               if (usefork == 0 && cmdentry.cmdtype == CMDNORMAL) {
                        pid_t   pid;
                        int serrno;
 
Index: options.h
===================================================================
RCS file: /cvsroot/src/bin/sh/options.h,v
retrieving revision 1.20
diff -u -u -r1.20 options.h
--- options.h   18 Jun 2011 21:18:46 -0000      1.20
+++ options.h   5 Jun 2014 15:43:29 -0000
@@ -99,9 +99,11 @@
 #define        cdprint optlist[17].val
 DEF_OPT( "tabcomplete",        0 )     /* <tab> causes filename expansion */
 #define        tabcomplete optlist[18].val
+DEF_OPT( "fork",       'F' )   /* use fork(2) instead of vfork(2) */
+#define        usefork optlist[19].val
 #ifdef DEBUG
 DEF_OPT( "debug",      0 )     /* enable debug prints */
-#define        debug optlist[19].val
+#define        debug optlist[20].val
 #endif
 
 #ifdef DEFINE_OPTIONS