libc: Implement nxtask_exit_cleanup

This runs the I/O and FILE cleanup procedures

libs/libc/stdlib/lib_exit.c

@@ -23,11 +23,18 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
+
 #include <stdlib.h>
 #include <unistd.h>
 
 #include "atexit.h"
 
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+void nxtask_exit_cleanup(int status);
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -38,5 +45,7 @@ void exit(int status)
 
   /* REVISIT: Need to flush files and streams */
 
+  nxtask_exit_cleanup(status);
+
   _exit(status);
 }

sched/task/exit.c

@@ -53,24 +53,24 @@
 
 void _exit(int status)
 {
-  up_exit(status);
+  up_exit(status & 0xff);
 }
 
 /****************************************************************************
- * Name: exit
+ * Name: nxtask_exit_cleanup
  *
  * Description:
- *   The exit() function causes normal process termination and the value of
- *   status & 0377 to be returned to the parent.
+ *   Perform cleanup before task is closed.
  *
- *   All functions registered with atexit() and on_exit() are called, in the
- *   reverse order of their registration.
+ *   If SCHED_ATEXIT or SCHED_ONEXIT are defined, all functions registered
+ *   with atexit() and on_exit() are called, in the reverse order of their
+ *   registration.
  *
  *   All open streams are flushed and closed.
  *
  ****************************************************************************/
 
-void exit(int status)
+void nxtask_exit_cleanup(int status)
 {
   FAR struct tcb_s *tcb = this_task();
 
@@ -101,10 +101,4 @@ void exit(int status)
    */
 
   nxtask_exithook(tcb, status, false);
-
-  /* Then "really" exit.  Only the lower 8 bits of the exit status are
-   * used.
-   */
-
-  _exit(status);
 }