Provide IRT process interface

src/untrusted/nacl/waitpid.c

+/*
+ * Copyright 2010 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 <sys/types.h>
+#include <sys/wait.h>
+#include <errno.h>
+
+#include "native_client/src/untrusted/nacl/nacl_irt.h"
+
+pid_t waitpid(pid_t pid, int *status, int options) {
+  if (__libnacl_irt_dev_process.waitpid == NULL) {
+    __libnacl_irt_process_init();
+    if (__libnacl_irt_dev_process.waitpid == NULL) {
+      errno = ENOSYS;
+      return -1;
+    }
+  }
+
+  int error = __libnacl_irt_dev_process.waitpid(&pid, status, options);
+  if (error) {
+    errno = error;
+    return -1;
+  }
+
+  return pid;
+}