add exit handler

src/call-exit-handler.c

@@ -0,0 +1,29 @@
+#include <libguile.h>
+#include <assert.h>
+
+#include "riverguile.h"
+
+static void *call_exit_handler_inner (void *data)
+{
+	assert(data == NULL);
+	return scm_call_0(context.exit_handler);
+}
+
+void *call_exit_handler (void)
+{
+	assert(context.exit_handler != NULL);
+
+	/* Continuation barrier causes stack unwind on exceptions (i.e. errors
+	 * in the user defined exit handler) to stop here. Otherwise the entire
+         * stack created by scm_with_guile() would be unwound. This makes
+         * responding to exceptions nicer.
+	 */
+	SCM call_result = scm_c_with_continuation_barrier(
+		call_exit_handler_inner, NULL
+	);
+
+	if ( call_result == NULL )
+		return (void *)"ERROR: An exception occured while calling the exit handler.\n";
+
+	return NULL;
+}