5.3.5/7 says: If the value of the operand of the delete-expression is not a null pointer value, the delete-expression will call a deallocation function (3.7.4.2). Otherwise, it is unspecified whether the deallocation function will be called. And 3.7.4.2/3 says: The value of the first argument supplied to a deallocation function may be a null pointer … Read more
nil is the literal null value for Objective-C objects, corresponding to the abstract type id or any Objective-C type declared via @interface. For instance: Nil is the literal null value for Objective-C classes, corresponding to the type Class. Since most code doesn’t need variables to reference classes, its use is not common. One example is: … Read more
You have to differentiate between cases: Variables can be undefined or undeclared. You’ll get an error if you access an undeclared variable in any context other than typeof. A variable that has been declared but not initialized is undefined. Undefined properties , like someExistingObj.someUndefProperty. An undefined property doesn’t yield an error and simply returns undefined, which, when converted to a boolean, evaluates to false. So, … Read more
As written, NULL isn’t defined in your program. Usually, that’s defined in a standard header file — specifically <cstddef> or <stddef.h>. Since you’re restricted to iostream, if yours doesn’t get NULL implicitly from that header, you can use 0 or, in C++11, nullptr, which is a keyword and doesn’t require a header. (It is not recommended to define NULL yourself. It might work sometimes, but it is technically … Read more
You can just check if the variable has a truthy value or not. That means will evaluate to true if value is not: null undefined NaN empty string (“”) 0 false The above list represents all possible falsy values in ECMA-/Javascript. Find it in the specification at the ToBoolean section. Furthermore, if you do not know whether a variable exists (that means, if it was declared) you should check with the typeof operator. For instance … Read more
References are not pointers. 8.3.2/1: A reference shall be initialized to refer to a valid object or function. [Note: in particular, a null reference cannot exist in a well-defined program, because the only way to create such a reference would be to bind it to the “object” obtained by dereferencing a null pointer, which causes … Read more
Why do we use NULL in strok() function? What does this program do when *h is pointing to a string?
It could be the encoding of the special characters. You could ask json_last_error() to get definite information. Update: The issue is solved, look at the “Solution” paragraph in the question.
The proper test is: This ensures that capital is always non null, when you perform the length check. Also, as the comments suggest, capital is null because you never initialize it.
The easiest way to check is entity == null. There is no shorter way to do that. Note that there is a method for this in the standard lib: Objects.isNull(Object obj) And another one which is the opposite of the above one: Objects.nonNull(Object obj) And there is yet another one which can be used to force … Read more