What do people find difficult about C pointers? [closed]

Answer 1

Once upon a time... We had 8 bit microprocessors and everyone wrote in assembly. Most processors included some type of indirect addressing used for jump tables and kernels. When higher level languages came along we add a thin layer of abstraction and called them pointers. Over the years we have gotten more and more away from the hardware. This is not necessarily a bad thing. They are called higher level languages for a reason. The more I can concentrate on what I want to do instead of the details of how it is done the better.

Answer 2

There is a great article supporting the notion that pointers are hard on Joel Spolsky's site - The Perils of JavaSchools.

[Disclaimer - I am not a Java-hater per se.]

Answer 3

Speaking as a C++ newbie here:

The pointer system took a while for me to digest not necessarily because of the concept but because of the C++ syntax relative to Java. A few things I found confusing are:

(1) Variable declaration:

A a(1);

vs.

A a = A(1);

vs.

A* a = new A(1); 

and apparently

A a(); 

is a function declaration and not a variable declaration. In other languages, there's basically just one way to declare a variable.

(2) The ampersand is used in a few different ways. If it is

int* i = &a;

then the &a is a memory address.

OTOH, if it is

void f(int &a) {}

then the &a is a passed-by-reference parameter.

Although this may seem trivial, it can be confusing for new users - I came from Java and Java's a language with a more uniform use of operators

(3) Array-pointer relationship

One thing that's a tad bit frustrating to comprehend is that a pointer

int* i

can be a pointer to an int

int *i = &n; // 

or

can be an array to an int

int* i = new int[5];

And then just to make things messier, pointers and array are not interchangeable in all cases and pointers cannot be passed as array parameters.

This sums up some of the basic frustrations I had with C/C++ and its pointers, which IMO, is greatly compounded by the fact that C/C++ has all these language-specific quirks.

Answer 4

The main difficulty with pointers, at least to me, is that I didn't start with C. I started with Java. The whole notion of pointers were really foreign until a couple of classes in college where I was expected to know C. So then I taught myself the very basics of C and how to use pointers in their very basic sense. Even then, every time I find myself reading C code, I have to look up pointer syntax.

So in my very limited experience(1 year real world + 4 in college), pointers confuse me because I've never had to really use it in anything other than a classroom setting. And I can sympathize with the students now starting out CS with JAVA instead of C or C++. As you said, you learned pointers in the 'Neolithic' age and have probably been using it ever since that. To us newer people, the notion of allocating memory and doing pointer arithmetic is really foreign because all these languages have abstracted that away.

P.S. After reading the Spolsky essay, his description of 'JavaSchools' was nothing like what I went through in college at Cornell ('05-'09). I took the structures and functional programming (sml), operating systems (C), algorithms (pen and paper), and a whole slew of other classes that weren't taught in java. However all the intro classes and electives were all done in java because there's value in not reinventing the wheel when you are trying to do something higher leveled than implementing a hashtable with pointers.

Answer 5

Here is a non-answer: Use cdecl (or c++decl) to figure it out:

eisbaw@leno:~$ cdecl explain 'int (*(*foo)(const void *))[3]'
declare foo as pointer to function (pointer to const void) returning pointer to array 3 of int

Answer 6

Pointers.. hah.. all about pointer in my head is that it give a memory address where the actual values of whatever its reference.. so no magic about it.. if you learn some assembly you wouldn't have that much trouble learning how pointers works.. come on guys... even in Java everything is a reference..