SyntaxFix

[c++] Using NULL in C++?

The downside of NULL in C++ is that it is a define for 0. This is a value that can be silently converted to pointer, a bool value, a float/double, or an int.

That is not very type safe and has lead to actual bugs in an application I worked on.

Consider this:

void Foo(int i);
void Foo(Bar* b);
void Foo(bool b);


main()
{
     Foo(0);         
     Foo(NULL); // same as Foo(0)
}

C++11 defines a nullptr that is convertible to a null pointer but not to other scalars. This is supported in all modern C++ compilers, including VC++ as of 2008. In older versions of GCC there is a similar feature, but then it was called __null.

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