[hackers] [st] Fix sigchld || Jochen Sprickerhof

[git]

commit 07ce96a3a0f4a650933f5f586082cbf2064ea2c1
Author: Jochen Sprickerhof <d...@jochen.sprickerhof.de>
Date:   Wed Apr 22 17:22:34 2015 +0200

    Fix sigchld
    
    Only wait for termination of the shell.

diff --git a/st.c b/st.c
index d954288..300cab6 100644
--- a/st.c
+++ b/st.c
@@ -1238,10 +1238,14 @@ execsh(void) {
 void
 sigchld(int a) {
        int stat, ret;
+       pid_t p;
 
-       if(waitpid(pid, &stat, 0) < 0)
+       if((p = waitpid(pid, &stat, WNOHANG)) < 0)
                die("Waiting for pid %hd failed: %s\n", pid, strerror(errno));
 
+       if(pid != p)
+               return;
+
        ret = WIFEXITED(stat) ? WEXITSTATUS(stat) : EXIT_FAILURE;
        if (ret != EXIT_SUCCESS)
                die("child finished with error '%d'\n", stat);