hush: make "wait %1" work even if the job is dead

Example script:

	sleep 1 | (sleep 1;exit 3) &
	sleep 2
	echo Zero:$?
	wait %1
	echo Three:$?

function                                             old     new   delta
clean_up_last_dead_job                                 -      24     +24
process_wait_result                                  426     447     +21
builtin_wait                                         285     293      +8
insert_job_into_table                                264     269      +5
builtin_jobs                                          68      73      +5
remove_job_from_table                                 59      57      -2
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 4/1 up/down: 63/-2)              Total: 61 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 52 insertions, 39 deletions

diff --git a/shell/hush.c b/shell/hush.c
index af5c26090..b76351fde 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -7237,11 +7237,42 @@ static const char *get_cmdtext(struct pipe *pi)
         return pi->cmdtext;
 }
 
+static void remove_job_from_table(struct pipe *pi)
+{
+        struct pipe *prev_pipe;
+
+        if (pi == G.job_list) {
+                G.job_list = pi->next;
+        } else {
+                prev_pipe = G.job_list;
+                while (prev_pipe->next != pi)
+                        prev_pipe = prev_pipe->next;
+                prev_pipe->next = pi->next;
+        }
+        G.last_jobid = 0;
+        if (G.job_list)
+                G.last_jobid = G.job_list->jobid;
+}
+
+static void delete_finished_job(struct pipe *pi)
+{
+        remove_job_from_table(pi);
+        free_pipe(pi);
+}
+
+static void clean_up_last_dead_job(void)
+{
+        if (G.job_list && !G.job_list->alive_cmds)
+                delete_finished_job(G.job_list);
+}
+
 static void insert_job_into_table(struct pipe *pi)
 {
         struct pipe *job, **jobp;
         int i;
 
+        clean_up_last_dead_job();
+
         /* Find the end of the list, and find next job ID to use */
         i = 0;
         jobp = &G.job_list;
@@ -7267,30 +7298,6 @@ static void insert_job_into_table(struct pipe *pi)
                 printf("[%u] %u %s\n", job->jobid, (unsigned)job->cmds[0].pid, job->cmdtext);
         G.last_jobid = job->jobid;
 }
-
-static void remove_job_from_table(struct pipe *pi)
-{
-        struct pipe *prev_pipe;
-
-        if (pi == G.job_list) {
-                G.job_list = pi->next;
-        } else {
-                prev_pipe = G.job_list;
-                while (prev_pipe->next != pi)
-                        prev_pipe = prev_pipe->next;
-                prev_pipe->next = pi->next;
-        }
-        if (G.job_list)
-                G.last_jobid = G.job_list->jobid;
-        else
-                G.last_jobid = 0;
-}
-
-static void delete_finished_job(struct pipe *pi)
-{
-        remove_job_from_table(pi);
-        free_pipe(pi);
-}
 #endif /* JOB */
 
 static int job_exited_or_stopped(struct pipe *pi)
@@ -7415,14 +7422,22 @@ static int process_wait_result(struct pipe *fg_pipe, pid_t childpid, int status)
                 pi->cmds[i].pid = 0;
                 pi->alive_cmds--;
                 if (!pi->alive_cmds) {
-                        if (G_interactive_fd)
+                        if (G_interactive_fd) {
                                 printf(JOB_STATUS_FORMAT, pi->jobid,
                                                 "Done", pi->cmdtext);
-                        delete_finished_job(pi);
-//bash deletes finished jobs from job table only in interactive mode, after "jobs" cmd,
-//or if pid of a new process matches one of the old ones
-//(see cleanup_dead_jobs(), delete_old_job(), J_NOTIFIED in bash source).
-//Testcase script: "(exit 3) & sleep 1; wait %1; echo $?" prints 3 in bash.
+                                delete_finished_job(pi);
+                        } else {
+/*
+ * bash deletes finished jobs from job table only in interactive mode,
+ * after "jobs" cmd, or if pid of a new process matches one of the old ones
+ * (see cleanup_dead_jobs(), delete_old_job(), J_NOTIFIED in bash source).
+ * Testcase script: "(exit 3) & sleep 1; wait %1; echo $?" prints 3 in bash.
+ * We only retain one "dead" job, if it's the single job on the list.
+ * This covers most of real-world scenarios where this is useful.
+ */
+                                if (pi != G.job_list)
+                                        delete_finished_job(pi);
+                        }
                 }
         } else {
                 /* child stopped */
@@ -9696,6 +9711,9 @@ static int FAST_FUNC builtin_jobs(char **argv UNUSED_PARAM)
 
                 printf(JOB_STATUS_FORMAT, job->jobid, status_string, job->cmdtext);
         }
+
+        clean_up_last_dead_job();
+
         return EXIT_SUCCESS;
 }
 
@@ -9939,17 +9957,12 @@ static int FAST_FUNC builtin_wait(char **argv)
                                 wait_pipe = parse_jobspec(*argv);
                                 if (wait_pipe) {
                                         ret = job_exited_or_stopped(wait_pipe);
-                                        if (ret < 0)
+                                        if (ret < 0) {
                                                 ret = wait_for_child_or_signal(wait_pipe, 0);
-//bash immediately deletes finished jobs from job table only in interactive mode,
-//we _always_ delete them at once. If we'd start keeping some dead jobs, this
-//(and more) would be necessary to avoid accumulating dead jobs:
-# if 0
-                                        else {
-                                                if (!wait_pipe->alive_cmds)
-                                                        delete_finished_job(wait_pipe);
+                                        } else {
+                                                /* waiting on "last dead job" removes it */
+                                                clean_up_last_dead_job();
                                         }
-# endif
                                 }
                                 /* else: parse_jobspec() already emitted error msg */
                                 continue;