wait4pid: if passed with pid < 0, do not set errno - it is already set by exec!

1 files changed, 33 insertions, 1 deletions

diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index 11dbb24fc..ff2b0bceb 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -61,11 +61,43 @@ pid_t spawn(char **argv)
 pid_t xspawn(char **argv)
 {
         pid_t pid = spawn(argv);
-        if (pid < 0) bb_perror_msg_and_die("%s", *argv);
+        if (pid < 0)
+                bb_perror_msg_and_die("%s", *argv);
         return pid;
 }
 
+// Wait for the specified child PID to exit, returning child's error return.
+int wait4pid(int pid)
+{
+        int status;
+
+        if (pid <= 0) {
+                /*errno = ECHILD; -- wrong. we expect errno to be set from failed exec */
+                return -1;
+        }
+        if (waitpid(pid, &status, 0) == -1)
+                return -1;
+        if (WIFEXITED(status))
+                return WEXITSTATUS(status);
+        if (WIFSIGNALED(status))
+                return WTERMSIG(status) + 10000;
+        return 0;
+}
 
+int wait_nohang(int *wstat)
+{
+        return waitpid(-1, wstat, WNOHANG);
+}
+
+int wait_pid(int *wstat, int pid)
+{
+        int r;
+
+        do
+                r = waitpid(pid, wstat, 0);
+        while ((r == -1) && (errno == EINTR));
+        return r;
+}
 
 #if 0 //ndef BB_NOMMU
 // Die with an error message if we can't daemonize.