43409: Fix process group setting in main shell.

A newly forked subshell now reports back the process group it
will be using for the main shell to record.

This prevents an error where the shell incorrectly thought an
exiting process owned the terminal and so grabbed it back,
putting the foreground process into the background.

3 files changed, 43 insertions, 21 deletions

diff --git a/ChangeLog b/ChangeLog
index 604170534..380c4df39 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2018-09-07  Peter Stephenson  <p.stephenson@samsung.com>
+
+	* 43409: Src/exec.c, Src/jobs.c: ensure main shell and newly
+	started subshell are agreed on which process group the latter
+	belongs to.
+
 2018-09-07  Daniel Shahaf  <d.s@daniel.shahaf.name>
 
 	* 43404 (after 43392): Doc/Makefile.in: Fix 'make install'
diff --git a/Src/exec.c b/Src/exec.c
index 09ee13209..074265f9f 100644
--- a/Src/exec.c
+++ b/Src/exec.c
@@ -994,9 +994,15 @@ enum {
     ESUB_JOB_CONTROL = 0x40
 };
 
+/*
+ * gleaderp may be NULL.  Otherwise, *gleaderp is set to point to the
+ * group leader of the job of the new process if this is assigned.  Else
+ * it is left alone: it is initialised to -1.
+ */
+
 /**/
 static void
-entersubsh(int flags)
+entersubsh(int flags, int *gleaderp)
 {
     int i, sig, monitor, job_control_ok;
 
@@ -1030,6 +1036,8 @@ entersubsh(int flags)
 		if (!(flags & ESUB_ASYNC))
 		    attachtty(jobtab[thisjob].gleader);
 	    }
+	    if (gleaderp)
+		*gleaderp = jobtab[list_pipe_job].gleader;
 	}
 	else if (!jobtab[thisjob].gleader ||
 		 setpgrp(0L, jobtab[thisjob].gleader) == -1) {
@@ -1050,6 +1058,8 @@ entersubsh(int flags)
 	    setpgrp(0L, jobtab[thisjob].gleader);
 	    if (!(flags & ESUB_ASYNC))
 		attachtty(jobtab[thisjob].gleader);
+	    if (gleaderp)
+		*gleaderp = jobtab[thisjob].gleader;
 	}
     }
     if (!(flags & ESUB_FAKE))
@@ -1682,7 +1692,7 @@ execpline(Estate state, wordcode slcode, int how, int last1)
 		    curjob = newjob;
 		    DPUTS(!list_pipe_pid, "invalid list_pipe_pid");
 		    addproc(list_pipe_pid, list_pipe_text, 0,
-			    &list_pipe_start);
+			    &list_pipe_start, -1);
 
 		    /* If the super-job contains only the sub-shell, the
 		       sub-shell is the group leader. */
@@ -1818,7 +1828,7 @@ execpline(Estate state, wordcode slcode, int how, int last1)
 		    }
 		    else {
 			close(synch[0]);
-			entersubsh(ESUB_ASYNC);
+			entersubsh(ESUB_ASYNC, NULL);
 			/*
 			 * At this point, we used to attach this process
 			 * to the process group of list_pipe_job (the
@@ -2175,7 +2185,7 @@ closemn(struct multio **mfds, int fd, int type)
 	    }
 	    mn->ct = 1;
 	    mn->fds[0] = fd;
-	    addproc(pid, NULL, 1, &bgtime);
+	    addproc(pid, NULL, 1, &bgtime, -1);
 	    child_unblock();
 	    return;
 	}
@@ -2676,7 +2686,7 @@ execcmd_fork(Estate state, int how, int type, Wordcode varspc,
 {
     pid_t pid;
     int synch[2], flags;
-    char dummy;
+    int gleader = -1;
     struct timeval bgtime;
 
     child_block();
@@ -2693,7 +2703,7 @@ execcmd_fork(Estate state, int how, int type, Wordcode varspc,
     }
     if (pid) {
 	close(synch[1]);
-	read_loop(synch[0], &dummy, 1);
+	read_loop(synch[0], (char *)&gleader, sizeof(gleader));
 	close(synch[0]);
 	if (how & Z_ASYNC) {
 	    lastpid = (zlong) pid;
@@ -2711,7 +2721,7 @@ execcmd_fork(Estate state, int how, int type, Wordcode varspc,
 		      3 : WC_ASSIGN_NUM(ac) + 2);
 	    }
 	}
-	addproc(pid, text, 0, &bgtime);
+	addproc(pid, text, 0, &bgtime, gleader);
 	if (oautocont >= 0)
 	    opts[AUTOCONTINUE] = oautocont;
 	pipecleanfilelist(jobtab[thisjob].filelist, 1);
@@ -2726,7 +2736,8 @@ execcmd_fork(Estate state, int how, int type, Wordcode varspc,
     if (type == WC_SUBSH && !(how & Z_ASYNC))
 	flags |= ESUB_JOB_CONTROL;
     *filelistp = jobtab[thisjob].filelist;
-    entersubsh(flags);
+    entersubsh(flags, &gleader);
+    write(synch[1], &gleader, sizeof(gleader));
     close(synch[1]);
     zclose(close_if_forked);
 
@@ -3842,7 +3853,7 @@ execcmd_exec(Estate state, Execcmd_params eparams,
 	    if ((do_exec || (type >= WC_CURSH && last1 == 1))
 		&& !forked)
 		flags |= ESUB_REVERTPGRP;
-	    entersubsh(flags);
+	    entersubsh(flags, NULL);
 	}
 	if (type == WC_FUNCDEF) {
 	    Eprog redir_prog;
@@ -4604,7 +4615,7 @@ getoutput(char *cmd, int qt)
     child_unblock();
     zclose(pipes[0]);
     redup(pipes[1], 1);
-    entersubsh(ESUB_PGRP|ESUB_NOMONITOR);
+    entersubsh(ESUB_PGRP|ESUB_NOMONITOR, NULL);
     cmdpush(CS_CMDSUBST);
     execode(prog, 0, 1, "cmdsubst");
     cmdpop();
@@ -4798,7 +4809,7 @@ getoutputfile(char *cmd, char **eptr)
 
     /* pid == 0 */
     redup(fd, 1);
-    entersubsh(ESUB_PGRP|ESUB_NOMONITOR);
+    entersubsh(ESUB_PGRP|ESUB_NOMONITOR, NULL);
     cmdpush(CS_CMDSUBST);
     execode(prog, 0, 1, "equalsubst");
     cmdpop();
@@ -4865,7 +4876,7 @@ getproc(char *cmd, char **eptr)
 	if (pid == -1)
 	    return NULL;
 	if (!out)
-	    addproc(pid, NULL, 1, &bgtime);
+	    addproc(pid, NULL, 1, &bgtime, -1);
 	procsubstpid = pid;
 	return pnam;
     }
@@ -4875,7 +4886,7 @@ getproc(char *cmd, char **eptr)
 	zerr("can't open %s: %e", pnam, errno);
 	_exit(1);
     }
-    entersubsh(ESUB_ASYNC|ESUB_PGRP);
+    entersubsh(ESUB_ASYNC|ESUB_PGRP, NULL);
     redup(fd, out);
 #else /* PATH_DEV_FD */
     int pipes[2], fd;
@@ -4902,12 +4913,12 @@ getproc(char *cmd, char **eptr)
 	addfilelist(NULL, fd);
 	if (!out)
 	{
-	    addproc(pid, NULL, 1, &bgtime);
+	    addproc(pid, NULL, 1, &bgtime, -1);
 	}
 	procsubstpid = pid;
 	return pnam;
     }
-    entersubsh(ESUB_ASYNC|ESUB_PGRP);
+    entersubsh(ESUB_ASYNC|ESUB_PGRP, NULL);
     redup(pipes[out], out);
     closem(FDT_UNUSED, 0);   /* this closes pipes[!out] as well */
 #endif /* PATH_DEV_FD */
@@ -4954,11 +4965,11 @@ getpipe(char *cmd, int nullexec)
 	    return -1;
 	}
 	if (!nullexec)
-	    addproc(pid, NULL, 1, &bgtime);
+	    addproc(pid, NULL, 1, &bgtime, -1);
 	procsubstpid = pid;
 	return pipes[!out];
     }
-    entersubsh(ESUB_PGRP);
+    entersubsh(ESUB_PGRP, NULL);
     redup(pipes[out], out);
     closem(FDT_UNUSED, 0);	/* this closes pipes[!out] as well */
     cmdpush(CS_CMDSUBST);
diff --git a/Src/jobs.c b/Src/jobs.c
index 38b3d896b..ba87a17fa 100644
--- a/Src/jobs.c
+++ b/Src/jobs.c
@@ -1375,7 +1375,7 @@ deletejob(Job jn, int disowning)
 
 /**/
 void
-addproc(pid_t pid, char *text, int aux, struct timeval *bgtime)
+addproc(pid_t pid, char *text, int aux, struct timeval *bgtime, int gleader)
 {
     Process pn, *pnlist;
 
@@ -1392,10 +1392,15 @@ addproc(pid_t pid, char *text, int aux, struct timeval *bgtime)
     if (!aux)
     {
 	pn->bgtime = *bgtime;
-	/* if this is the first process we are adding to *
-	 * the job, then it's the group leader.          */
+	/*
+	 * if this is the first process we are adding to
+	 * the job, then it's the group leader.
+	 *
+	 * Exception: if the forked subshell reported its own group
+	 * leader, set that.
+	 */
 	if (!jobtab[thisjob].gleader)
-	    jobtab[thisjob].gleader = pid;
+	    jobtab[thisjob].gleader = (gleader != -1) ? gleader : pid;
 	/* attach this process to end of process list of current job */
 	pnlist = &jobtab[thisjob].procs;
     }