sig_tstp: Use _exit() rather than exit().

src/osdep/signals.c

@@ -78,7 +78,12 @@ sig_tstp(struct terminal *term)
 	if (!fork()) {
 		sleep(1);
 		kill(pid, SIGCONT);
-		exit(0);
+		/* Use _exit() rather than exit(), so that atexit
+		 * functions are not called, and stdio output buffers
+		 * are not flushed.  Any such things must have been
+		 * inherited from the parent process, which will take
+		 * care of them when appropriate.  */
+		_exit(0);
 	}
 #endif
 	raise(SIGSTOP);