Merge bitcoin#11066: Document the preference of nullptr over NULL or …

…(void*)0

bea8e9e Document the preference of nullptr over NULL or (void*)0 (practicalswift)

Pull request description:

  Document the preference of `nullptr` over `NULL` or `(void*)0`.

  After this commit:

  ```
  $ git grep "[^A-Za-z_]NULL[^A-Za-z_]" | grep -vE '(leveldb|univalue|secp256k1|torcontrol|NULL certificates|ctaes|release-notes|patches|configure.ac|developer-notes)'
  $
  ```

  Some context:
  * `NULL → nullptr` was handled in the recently merged PR bitcoin#10483
  * `0 → nullptr` was handled in the recently merged PR bitcoin#10645

Tree-SHA512: f863096aa4eb21705910f89713ca9cc0d83c6df2147e3d3530c3e1589b96f6c68de8755dcf37d8ce99ebda3cfb69805e00eab13bf65424aaf16170e9dda3958a

doc/developer-notes.md

@@ -37,6 +37,7 @@ code.
 
 - **Miscellaneous**
   - `++i` is preferred over `i++`.
+  - `nullptr` is preferred over `NULL` or `(void*)0`.
   - `static_assert` is preferred over `assert` where possible. Generally; compile-time checking is preferred over run-time checking.
   - Align pointers and references to the left i.e. use `type& var` and not `type &var`.
 
@@ -288,7 +289,7 @@ Wallet
 
   - *Rationale*: In RPC code that conditionally uses the wallet (such as
     `validateaddress`) it is easy to forget that global pointer `pwalletMain`
-    can be NULL. See `test/functional/disablewallet.py` for functional tests
+    can be nullptr. See `test/functional/disablewallet.py` for functional tests
     exercising the API with `-disablewallet`
 
 - Include `db_cxx.h` (BerkeleyDB header) only when `ENABLE_WALLET` is set

src/qt/macdockiconhandler.mm

@@ -18,7 +18,7 @@
 extern void qt_mac_set_dock_menu(QMenu *);
 #endif
 
-static MacDockIconHandler *s_instance = NULL;
+static MacDockIconHandler *s_instance = nullptr;
 
 bool dockClickHandler(id self,SEL _cmd,...) {
     Q_UNUSED(self)
@@ -34,7 +34,7 @@ void setupDockClickHandler() {
     Class cls = objc_getClass("NSApplication");
     id appInst = objc_msgSend((id)cls, sel_registerName("sharedApplication"));
 
-    if (appInst != NULL) {
+    if (appInst != nullptr) {
         id delegate = objc_msgSend(appInst, sel_registerName("delegate"));
         Class delClass = (Class)objc_msgSend(delegate,  sel_registerName("class"));
         SEL shouldHandle = sel_registerName("applicationShouldHandleReopen:hasVisibleWindows:");
@@ -53,7 +53,7 @@ void setupDockClickHandler() {
     setupDockClickHandler();
     this->m_dummyWidget = new QWidget();
     this->m_dockMenu = new QMenu(this->m_dummyWidget);
-    this->setMainWindow(NULL);
+    this->setMainWindow(nullptr);
 #if QT_VERSION < 0x050000
     qt_mac_set_dock_menu(this->m_dockMenu);
 #elif QT_VERSION >= 0x050200
@@ -69,7 +69,7 @@ void setupDockClickHandler() {
 MacDockIconHandler::~MacDockIconHandler()
 {
     delete this->m_dummyWidget;
-    this->setMainWindow(NULL);
+    this->setMainWindow(nullptr);
 }
 
 QMenu *MacDockIconHandler::dockMenu()

src/qt/macnotificationhandler.mm

@@ -75,7 +75,7 @@ - (NSString *)__bundleIdentifier
 
 MacNotificationHandler *MacNotificationHandler::instance()
 {
-    static MacNotificationHandler *s_instance = NULL;
+    static MacNotificationHandler *s_instance = nullptr;
     if (!s_instance) {
         s_instance = new MacNotificationHandler();