Provide IRT process interface

src/untrusted/nacl/signal.c

Index: src/untrusted/nacl/signal.c
diff --git a/src/untrusted/nacl/signal.c b/src/untrusted/nacl/signal.c
new file mode 100644
index 0000000000000000000000000000000000000000..425af3daaec9d1a055c03416a4b8e5005e122620
--- /dev/null
+++ b/src/untrusted/nacl/signal.c
@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2013 The Native Client Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include <errno.h>
+#include <signal.h>
+#include <sys/types.h>
+
+#include "native_client/src/untrusted/nacl/nacl_irt.h"
+
+sighandler_t signal(int sig, sighandler_t handler) {
+  if (!__libnacl_irt_init_fn(&__libnacl_irt_dev_process.signal,
+                             __libnacl_irt_dev_process_init)) {
+    return -1;
+  }
+
+  sighandler_t oldhandler;
+  int error = __libnacl_irt_dev_process.signal(sig, handler, &oldhandler);
+  if (error) {
+    errno = error;
+    return SIG_ERR;
+  }
+
+  return oldhandler;
+}