What is the difference between

• the stack and the heap,
• malloc, new, new[],
• free, delete, delete[]
• pointers, references and pointers-to-pointers. When do you use which?

Obviously, these are fundamental aspects of C++ programming, but that is why every good C++ programmer has to know the answers to these.

Very good answers are given in:

• http://stackoverflow.com/questions/79923/what-and-where-are-the-stack-and-heap/79936#79936
  • I'd expect a programmer to come up with basically all of these points
• http://stackoverflow.com/questions/240212/what-is-the-difference-between-new-delete-and-malloc-free/240308#240308
  • malloc/free, new/delete have to be paired correctly, malloc allocates raw block of memory, new constructs object of specified type
• http://stackoverflow.com/questions/57483/difference-between-pointer-variable-and-reference-variable-in-c
  • pointers can point to NULL/be uninitialized, references are always initialized, pointers can be reassigned i.e. made to point to another object

A bit meta, but I think still worthwhile: "What are the questions every good C/C++ Developer should be able to answer?" :)

I'm serious - a good developer should be able to suggest these.

Q: How does a pointer point to an object?

A: The pointer stores the address of that object.

Usual answer is "emmmm, it... well... points..." which is pointless.

What can happen if your destructor isn't virtual?

C++ :

What are Virtual Constructors in C++? :P

P.S : Notice the smiley

C (also a valid C++ question)

What's wrong with the following code?

char *p = "Sam";
p[0] = 'R';

Explain when you would use a std::vector; a std::map; a std::list and so on.

Explain the different types of casting and how they are applied in the real world.

Why

void strcpy(char* dest, char* src)
{
    while(*dest++ = *src++);
}

copies the entire src string to destination?

The question was about good C/C++ programmers :)

They are different languages, C and C++. "C/C++" is a wrong term.

My favorite question when I interview people: "What is a difference between a copy constructor and an assignment operator?"

Why would you choose C over more modern languages?

How would you go about implementing a template function for swapping two variables?

How will you access tenth element of an array without using square brackets?

Interesting question I just saw:

What’s the auto keyword good for?

How would you implement a working binary search? This goes for any serious programmer, I think.

PS: This question isn't really C++ specific, but I found this to be a shockingly good interview question. The concept of binary search is so simple that everybody should know it and everybody should be able to derive a working implementation from this concept.

• How do you know malloc() fails? How do you know new fails?
• What are binary files and text files?

For C++ developers:

Given class A

class A 
{
public:
    A();
    ~A();

    A operator=(A an_a);
private:
    int  i;
}

A::A()
{
}

A::~A()
{
}

A A::operator=(A an_a)
{
    i = an_a.i;
}

1) How many A's will be created by the following

   {
      A  a1, a2;

      a1 = a2;
   }

2) Why won't the code compile?

3) What's the value of i in a1 from above?

4) What's wrong with the operator= method?

5) (refinement of question from above) What is special about a static method?

class A
{
...
};

A a[5];

How many times A's constructor would be called?

What is the difference between static in C and static in C++

A questions about Virtual Destructor, why you need them etc, or a questions about why a bit of code does not work, when the need for a Virtual Destructor is part of the answer.

Also a question on when it is better to use Java and/or C# than C++, e.g does the person know what an garbage collector is.

Most asked question in embedded companies... 1. what is the major difference b/w structure and union? 2. what is Dangling pointer? 3. Memory leakage???

More questions will be like this only....

which containers are provided by STL and in which scenario you would use a particular container.

I think this really goes for all programming languages, but that being said I think if you program C, C++ you should be able:

1. Implement a recursive algorithm (or multiple different types, tail recursion etc.)
2. Explain their affect on program execution and memory (Stack allocation etc.).

• What is function overloading and operator overloading?
• What is a friend class?

I liked this one: http://stackoverflow.com/questions/3931156/algorithm-interview-question

It's not enough just to know algorithms. Programming is about making decisions.

Q: Differentiate C, C++, and C#.

A: Googles....

My favorite: how do you declare a pointer to a function returning void and taking two pointers to void as parameters?

Which debugging tool do you use?

Explain how (break points) or (memory leak detection) work in debugging tools.

How can you speed up compile time?

Any experienced C/C++ programmer will be able to talk about how to arrange header files etc so as to reduce the number of header files that need to be read. This then leads into some questions about good design etc…

You can ask the candidate how would they implement an algorithm in C and later how would they do the same in C++ making use of the STL.

You can ask why did he/she choose C or C++ for the projects they've done and also ask how would they approach if the C projects had to be done in C++ and vice versa.

Well for a start I wouldn't ask questions whose answers can be found easily in a C or C++ reference manual or with a simple Google search unless the job for which they were being interviewed forbade using those resources (in which case the successful candidate will come to wish he wasn't).

Go for more high level questions with less clear cut or even controversial answers.

e.g. I might ask

what are some of the disadvantages of C or C++ as compared to (say) Java?

what strategies might you use to mitigate the disadvantages?

under what circumstances do the disadvantages become advantages?

Just what is a protected abstract virtual base pure virtual private destructor? -- Tom Cargill

Most people might not be able to answer it, but hopefully most will give it a good thought.

How can you effectively manage the memory? Can you show me through some examples...

And obviously looking for smart pointers usage..

• When to use friend-classes?
• When do Destructors have to be virtual and what is the difference to nonvirtual Dtors?
• What do Smart-Pointers do and which types of Smartpointers exist (aiming towards shared/scoped)

There are a lot of questions which could be formulated by simply changing the tasks of C++ FAQ lite into questions: C++ FAQ lite ^[1]

How to declare and initialize an int pointer to a specific memory address like 0x604768, and make it store the value 0xdead?

int* address = (int*)(void*)(uintptr_t)0x604768;
printf("Memory address is: 0x%p \n", address);

*address = 0xdead;
printf("Content of that address is: 0x%p \n", *address);