Change wording of EOF behaviour in stage_1

helpers/harness.tcl

@@ -168,5 +168,6 @@ while {![eof $test_file]} {
 }
 
 # Calling close causes zsh to exit unhappily, so we send ^D instead.
+puts "Sending ^D to shell to exit"
 send -s "\x04"
 if {0 != [wait_for_exit]} {error "shell didn't exit cleanly"}

helpers/timeout.c

@@ -33,6 +33,11 @@ static void kill_em_all(int _)
 {
     (void)_;
     kill(pid, SIGTERM);
+    // In general, it's a Very Bad Idea to printf inside of a signal handler.
+    // However, since we're immediatly exiting, it is acceptable in this case.
+    // See https://www.securecoding.cert.org/confluence/display/c/SIG30-C.+Call+only+asynchronous-safe+functions+within+signal+handlers
+    // for more information on what isn't safe to do in signal handlers.
+    printf("Killing process %d due to timeout\n", pid);
     exit(1);
 }
 

stage_1.md

@@ -39,7 +39,7 @@ You should
    itself instead of executing an external program), call it;
    otherwise
  - execute that as a command with space-delimited arguments;
- - repeat until you receive EOF on `stdin`.
+ - when you receive EOF on `stdin` instead of a command, exit.
 
 ### Executing a command