gpgscm: Implement 'atexit'.

* tests/gpgscm/ffi.scm (throw): Run *run-atexit-handlers* when
terminating the interpreter.
(*atexit-handlers*): New variable.
(*run-atexit-handlers*): New function.
(atexit): Likewise.
* tests/gpgscm/main.c (main): Run *run-atexit-handlers* at normal
interpreter shutdown.

Signed-off-by: Justus Winter <justus@g10code.com>

tests/gpgscm/ffi.scm

@@ -57,6 +57,7 @@
    ((more-handlers?)
     (apply (pop-handler) x))
    ((and (= 2 (length x)) (equal? *interpreter-exit* (car x)))
+    (*run-atexit-handlers*)
     (_exit (cadr x)))
    (else
     (apply error x))))
@@ -64,3 +65,20 @@
 ;; Terminate the process returning STATUS to the parent.
 (define (exit status)
   (throw *interpreter-exit* status))
+
+;; A list of functions run at interpreter shutdown.
+(define *atexit-handlers* (list))
+
+;; Execute all these functions.
+(define (*run-atexit-handlers*)
+  (unless (null? *atexit-handlers*)
+	  (let ((proc (car *atexit-handlers*)))
+	    ;; Drop proc from the list so that it will not get
+	    ;; executed again even if it raises an exception.
+	    (set! *atexit-handlers* (cdr *atexit-handlers*))
+	    (proc)
+	    (*run-atexit-handlers*))))
+
+;; Register a function to be run at interpreter shutdown.
+(define (atexit proc)
+  (set! *atexit-handlers* (cons proc *atexit-handlers*)))

tests/gpgscm/main.c

@@ -291,6 +291,7 @@ main (int argc, char **argv)
         log_fatal ("%s: %s", script, gpg_strerror (err));
     }
 
+  scheme_load_string (sc, "(*run-atexit-handlers*)");
   scheme_deinit (sc);
   xfree (sc);
   return EXIT_SUCCESS;