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This might look like a smart way to assign the return value of malloc to ptr and check if it is NULL in one step, but the malloc call and the assignment to ptr is a side effect of evaluating the expression that forms the assert condition.
In computer programming, lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed.
Used in FreeBSD's PHK malloc(3) for debugging when /etc/malloc.conf is symlinked to "-J" to initialize all newly allocated memory as this value is not a NULL pointer or ASCII NUL character. ABABABAB: Used by Microsoft's debug HeapAlloc() to mark "no man's land" guard bytes after allocated heap memory. [26] ABADBABE
Some features of C++ that promote more type-safe code: The new operator returns a pointer of type based on operand, whereas malloc returns a void pointer. C++ code can use virtual functions and templates to achieve polymorphism without void pointers. Safer casting operators, such as dynamic cast that performs run-time type checking.
Another frequent source of dangling pointers is a jumbled combination of malloc() and free() library calls: a pointer becomes dangling when the block of memory it points to is freed. As with the previous example one way to avoid this is to make sure to reset the pointer to null after freeing its reference—as demonstrated below.
A null pointer has a value reserved for indicating that the pointer does not refer to a valid object. Null pointers are routinely used to represent conditions such as the end of a list of unknown length or the failure to perform some action; this use of null pointers can be compared to nullable types and to the Nothing value in an option type.
In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
C uses the malloc function; C++ and Java use the new operator; and many other languages (such as Python) allocate all objects from the free store. Determining when an object ought to be created ( object creation ) is generally trivial and unproblematic, though techniques such as object pools mean an object may be created before immediate use.