Change startup ABI for untrusted code to be C-compatible

src/untrusted/nacl/start.c

+/*
+ * Copyright (c) 2011 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 <unistd.h>
+
+#include "native_client/src/include/elf32.h"
+#include "native_client/src/untrusted/nacl/nacl_irt.h"
+#include "native_client/src/untrusted/nacl/nacl_startup.h"
+
+
+void __libc_init_array(void);
+void __libc_fini_array(void);
+
+void __pthread_initialize(void);
+void __pthread_shutdown(void);
+
+int main(int argc, char **argv, char **envp);
+
+/*
+ * This is the true entry point for untrusted code.
+ * See nacl_startup.h for the layout at the argument pointer.
+ */
+void _start(uint32_t *info) {
+  void (*fini)(void) = nacl_startup_fini(info);
+  int argc = nacl_startup_argc(info);
+  char **argv = nacl_startup_argv(info);
+  char **envp = nacl_startup_envp(info);
+  Elf32_auxv_t *auxv = nacl_startup_auxv(info);
+
+  environ = envp;
+
+  __libnacl_irt_init(auxv);
+
+  /*
+   * If we were started by a dynamic linker, then it passed its finalizer
+   * function here.  For static linking, this is always NULL.
+   */
+  if (fini != NULL)
+    atexit(fini);
+
+  atexit(&__libc_fini_array);
+
+  __pthread_initialize();
+  atexit(&__pthread_shutdown);
+
+  __libc_init_array();
+
+  exit(main(argc, argv, envp));
+
+  /*NOTREACHED*/
+  while (1) *(volatile int *) 0;  /* Crash.  */
+}