C++11 declares a type safe null pointer

content/common/set_process_title_linux.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file implements BSD-style setproctitle() for Linux.
 // It is written such that it can easily be compiled outside Chromium.
 //
 // The Linux kernel sets up two locations in memory to pass arguments and
 // environment variables to processes. First, there are two char* arrays stored
 // one after another: argv and environ. A pointer to argv is passed to main(),
 // while glibc sets the global variable |environ| to point at the latter. Both
-// of these arrays are terminated by a NULL pointer; the environment array is
+// of these arrays are terminated by a nullptr pointer; the environment array is
 // also followed by some empty space to allow additional variables to be added.
 //
 // These arrays contain pointers to a second location in memory, where the
 // strings themselves are stored one after another: first all the arguments,
 // then the environment variables. The kernel will allocate a single page of
 // memory for this purpose, so the end of the page containing argv[0] is the
 // end of the storage potentially available to store the process title.
 //
 // When the kernel reads the command line arguments for a process, it looks at
 // the range of memory within this page that it initially used for the argument
@@ skipping 17 matching lines @@
 #include "content/common/set_process_title_linux.h"
 
 #include <stdarg.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
 
 extern char** environ;
 
-static char** g_main_argv = NULL;
-static char* g_orig_argv0 = NULL;
+static char** g_main_argv = nullptr;
+static char* g_orig_argv0 = nullptr;
 
 void setproctitle(const char* fmt, ...) {
   va_list ap;
   size_t i, avail_size;
   uintptr_t page_size, page, page_end;
   // Sanity check before we try and set the process title.
-  // The BSD version allows fmt == NULL to restore the original title.
+  // The BSD version allows fmt == nullptr to restore the original title.
   if (!g_main_argv || !environ || !fmt)
     return;
   if (!g_orig_argv0) {
     // Save the original argv[0].
     g_orig_argv0 = strdup(g_main_argv[0]);
     if (!g_orig_argv0)
       return;
   }
   page_size = sysconf(_SC_PAGESIZE);
   // Get the page on which the argument list and environment live.
@@ skipping 22 matching lines @@
   memset(g_main_argv[0], 0, avail_size);
   va_start(ap, fmt);
   if (fmt[0] == '-') {
     vsnprintf(g_main_argv[0], avail_size, &fmt[1], ap);
   } else {
     size_t size = snprintf(g_main_argv[0], avail_size, "%s ", g_orig_argv0);
     if (size < avail_size)
       vsnprintf(g_main_argv[0] + size, avail_size - size, fmt, ap);
   }
   va_end(ap);
-  g_main_argv[1] = NULL;
+  g_main_argv[1] = nullptr;
 }
 
 // A version of this built into glibc would not need this function, since
 // it could stash the argv pointer in __libc_start_main(). But we need it.
 void setproctitle_init(const char** main_argv) {
   if (g_main_argv)
     return;
 
   uintptr_t page_size = sysconf(_SC_PAGESIZE);
   // Check that the argv array is in fact on the same page of memory
   // as the environment array just as an added measure of protection.
   if (((uintptr_t) environ) / page_size == ((uintptr_t) main_argv) / page_size)
     g_main_argv = const_cast<char**>(main_argv);
 }