NaCl: Call __nacl_main in preference to main.

ChangeLog

@@ -1,3 +1,8 @@
+2015-08-25  Roland McGrath  <roland@hack.frob.com>
+
+	* sysdeps/nacl/start.c (_start): Call __nacl_main instead of main
+	if the weak reference is not null.
+
 2015-08-25  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* sysdeps/x86_64/strcmp.S: Remove "#if !IS_IN (libc)".

sysdeps/nacl/start.c

@@ -44,6 +44,10 @@
 /* The application defines this, of course.  */
 extern int main (int argc, char **argv, char **envp);
 
+/* But maybe it defines this too, in which case it takes precedence.  */
+extern int __nacl_main (int argc, char **argv, char **envp)
+  __attribute__ ((weak));
+
 /* These are defined in libc.  */
 extern int __libc_csu_init (int argc, char **argv, char **envp);
 extern void __libc_csu_fini (void);
@@ -59,7 +63,7 @@ _start (uint32_t info[])
 {
   /* The generic code actually assumes that envp follows argv.  */
 
-  __libc_start_main (&main,
+  __libc_start_main (&__nacl_main ?: &main,
 		     nacl_startup_argc (info),
 		     nacl_startup_argv (info),
 		     nacl_startup_auxv (info),