Cast pointers used with %p format strings to void *

tests/stack_alignment/stack_alignment_asm_test.c

 /*
  * Copyright (c) 2012 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 <assert.h>
 #include <sched.h>
 #include <stdint.h>
 #include <stdio.h>
@@ skipping 81 matching lines @@
   g_stack_ptr = stack_ptr;
   __libnacl_irt_thread.thread_exit((int32_t *) &g_stack_in_use);
 }
 
 int main(void) {
   __nc_initialize_interfaces();
 
   int offset;
   for (offset = 0; offset <= 32; offset++) {
     char *stack_top = stack + sizeof(stack) - offset;
-    printf("Checking offset %i: stack_top=%p...\n", offset, stack_top);
+    printf("Checking offset %i: stack_top=%p...\n", offset, (void *)stack_top);
     g_stack_ptr = NULL;
     g_stack_in_use = 1;
     void *dummy_tls = &dummy_tls;
     int rc = __libnacl_irt_thread.thread_create(ThreadStartWrapper, stack_top,
                                                 dummy_tls);
     assert(rc == 0);
     /* Spin until the thread exits. */
     while (g_stack_in_use) {
       sched_yield();
     }
-    printf("got g_stack_ptr=%p\n", g_stack_ptr);
+    printf("got g_stack_ptr=%p\n", (void *)g_stack_ptr);
     assert(g_stack_ptr <= stack_top);
     assert(((uintptr_t) g_stack_ptr + kStackPadBelowAlign) % kStackAlignment
            == 0);
   }
 
   return 0;
 }