Null Pointers
This article is quite advanced and assumes you have an understanding of C++. If not, please refer to the C++ section of this book!
nullptr is a keyword introduced in C++11 to represent a pointer that points to… well, nothing - It’s a constant that can be assigned to any pointer type to indicate that the pointer is not pointing to a valid memory location. Before the introduction of nullptr, programmers often used the integer constant 0 or the macro NULL to represent a null pointer. However, using nullptr is preferred.
Initializing a pointer without assigning it a specific address sets it to a null pointer.
int* nullPointer = nullptr;
Note that a nullptr is not implicitly convertible to integral types, which helps reduce the risk of accidental assignments or comparisons between pointers/integers/other objects.
Checking or Guarding for invalid pointers frequently in your code is good practice, especially when writing critical programs.
class SomeClass
{
public:
SomeClass(int val)
: data(val)
{
}
int data;
void PrintMe()
{
std::cout << "Data: " << data << std::endl;
}
};
int main()
{
SomeClass* somePtr = new SomeClass(69);
if (somePtr != nullptr)
{
somePtr->PrintMe();
}
else
{
// Throw some exception about the pointer being null
}
return 0;
}