*: code shrink and better "died from signal" reporting from wait4pid

function                                             old     new   delta
parse                                                964     967      +3
udhcp_run_script                                     670     665      -5
singlemount                                          911     906      -5
mount_it_now                                         360     355      -5
inotifyd_main                                        521     516      -5
xspawn                                                21       -     -21
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 1/4 up/down: 3/-41)             Total: -38 bytes

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

1 files changed, 6 insertions, 5 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 044d09047..72d6c7dc8 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -812,21 +812,22 @@ int bb_execvp(const char *file, char *const argv[]) FAST_FUNC;
 #define BB_EXECLP(prog,cmd,...) execlp(prog,cmd, __VA_ARGS__)
 #endif
 
-/* NOMMU friendy fork+exec */
+/* NOMMU friendy fork+exec: */
 pid_t spawn(char **argv) FAST_FUNC;
 pid_t xspawn(char **argv) FAST_FUNC;
 
 pid_t safe_waitpid(pid_t pid, int *wstat, int options) FAST_FUNC;
-/* Unlike waitpid, waits ONLY for one process.
+pid_t wait_any_nohang(int *wstat) FAST_FUNC;
+/* wait4pid: unlike waitpid, waits ONLY for one process.
+ * Returns sig + 0x180 if child is killed by signal.
  * It's safe to pass negative 'pids' from failed [v]fork -
  * wait4pid will return -1 (and will not clobber [v]fork's errno).
  * IOW: rc = wait4pid(spawn(argv));
  *      if (rc < 0) bb_perror_msg("%s", argv[0]);
- *      if (rc > 0) bb_error_msg("exit code: %d", rc);
+ *      if (rc > 0) bb_error_msg("exit code: %d", rc & 0xff);
  */
 int wait4pid(pid_t pid) FAST_FUNC;
-pid_t wait_any_nohang(int *wstat) FAST_FUNC;
-/* wait4pid(spawn(argv)) + NOFORK/NOEXEC (if configured) */
+/* Same as wait4pid(spawn(argv)), but with NOFORK/NOEXEC if configured: */
 int spawn_and_wait(char **argv) FAST_FUNC;
 struct nofork_save_area {
         jmp_buf die_jmp;