access: various idioms

Author: leogermond

courses/fundamentals_of_ada/140_access_types/11-idiom-constant-pointer.rst

@@ -0,0 +1,49 @@
+=================
+Protecting Access
+=================
+
+------------------------------
+Elaboration Dynamic Allocation
+------------------------------
+
+1. Deallocations can cause leaks, corruption
+
+    - |rightarrow| Disallow them entirely
+
+2. A dynamically allocated object needs to be deallocated
+
+    - |rightarrow| Unless it is global
+
+* |rightarrow| Allow only allocation onto globals
+
+    - And restrict them to program elaboration
+
+--------------------------------
+Constant Access at Library Level
+--------------------------------
+
+.. code:: Ada
+
+   type Acc is access T;
+   procedure Free is new Ada.Unchecked_Deallocation (T, Acc);
+
+   A : constant Acc := new T;
+
+* :ada:`A` is :ada:`constant`
+
+    * Cannot be deallocated
+
+-------------------------------
+Constant Access as Discriminant
+-------------------------------
+
+.. code:: Ada
+
+   type R (A : access T) is limited record
+
+* :ada:`A` is :ada:`constant`
+
+    * Cannot be deallocated
+
+* :ada:`R` is :ada:`limited`, cannot be copied
+