Switch wait command to use topics

Prior to this fix, the wait command used waitpid() directly. Switch it to
calling process_mark_finished_children() along with the rest of the job
machinery. This centralizes the waitpid call to a single location.

src/builtin_wait.cpp

@@ -6,6 +6,7 @@
 #include "builtin_wait.h"
 #include "common.h"
 #include "proc.h"
+#include "reader.h"
 #include "wgetopt.h"
 #include "wutil.h"
 
@@ -73,10 +74,10 @@ static int wait_for_backgrounds(bool any_flag) {
     size_t jobs_len = jobs.count();
 
     while ((!any_flag && !all_jobs_finished()) || (any_flag && !any_jobs_finished(jobs_len))) {
-        pid_t pid = proc_wait_any();
-        if (pid == -1 && errno == EINTR) {
+        if (reader_test_interrupted()) {
             return 128 + SIGINT;
         }
+        proc_wait_any();
     }
     return 0;
 }
@@ -112,10 +113,10 @@ static bool any_specified_jobs_finished(const std::vector<job_id_t> &ids) {
 static int wait_for_backgrounds_specified(const std::vector<job_id_t> &ids, bool any_flag) {
     while ((!any_flag && !all_specified_jobs_finished(ids)) ||
            (any_flag && !any_specified_jobs_finished(ids))) {
-        pid_t pid = proc_wait_any();
-        if (pid == -1 && errno == EINTR) {
+        if (reader_test_interrupted()) {
             return 128 + SIGINT;
         }
+        proc_wait_any();
     }
     return 0;
 }

src/proc.cpp

@@ -983,13 +983,10 @@ void proc_pop_interactive() {
     if (is_interactive != old) signal_set_handlers();
 }
 
-pid_t proc_wait_any() {
-    int pid_status;
-    pid_t pid = waitpid(-1, &pid_status, WUNTRACED);
-    if (pid == -1) return -1;
-    handle_child_status(pid, proc_status_t::from_waitpid(pid_status));
+void proc_wait_any() {
+    ASSERT_IS_MAIN_THREAD();
+    process_mark_finished_children(true /* block_ok */);
     process_clean_after_marking(is_interactive);
-    return pid;
 }
 
 void hup_background_jobs() {

src/proc.h

@@ -542,8 +542,8 @@ void proc_push_interactive(int value);
 /// Set is_interactive flag to the previous value. If needed, update signal handlers.
 void proc_pop_interactive();
 
-/// Wait for any process finishing.
-pid_t proc_wait_any();
+/// Wait for any process finishing, or receipt of a signal.
+void proc_wait_any();
 
 /// Set and get whether we are in initialization.
 // Hackish. In order to correctly report the origin of code with no associated file, we need to

src/reader.cpp

@@ -797,6 +797,8 @@ bool reader_data_t::expand_abbreviation_as_necessary(size_t cursor_backtrack) {
 
 void reader_reset_interrupted() { interrupted = 0; }
 
+bool reader_test_interrupted() { return interrupted != 0; }
+
 bool reader_test_and_clear_interrupted() {
     int res = interrupted;
     if (res) {

src/reader.h

@@ -121,6 +121,9 @@ size_t reader_get_cursor_pos();
 /// selection, true otherwise.
 bool reader_get_selection(size_t *start, size_t *len);
 
+/// Return the value of the interrupted flag, which is set by the sigint handler.
+bool reader_test_interrupted();
+
 /// Return the value of the interrupted flag, which is set by the sigint handler, and clear it if it
 /// was set.
 bool reader_test_and_clear_interrupted();