How much memory is required to represent the address?

Question

Consider the following code snippet.

int var; cout << (long)&var; 

My doubt is how we know that long int is wide enough to hold the memory location indicated by &var . What if this is not enough?

The complete code that I am executing ...

 //: C03:YourPets2.cpp // From Thinking in C++, 2nd Edition // Available at http://www.BruceEckel.com // (c) Bruce Eckel 2000 // Copyright notice in Copyright.txt #include <iostream> using namespace std; int dog, cat, bird, fish; void f(int pet) { cout << "pet id number: " << pet << endl; } int main() { int i, j, k; cout << "Address size " << sizeof(&f) << endl; cout << "Long size " << sizeof(long) << endl; cout << "Intptr size " << sizeof(intptr_t) << endl; cout << "f(): " << &f << endl; cout << "f(): " << (long)&f << endl; cout << "f(): " << (long long)&f << endl; cout << "dog: " << (long)&dog << endl; cout << "cat: " << &cat << endl; cout << "bird: " << &bird << endl; cout << "fish: " << (long)&fish << endl; cout << "i: " << (long)&i << endl; cout << "i: " << (long long)&i << endl; cout << "j: " << (long)&j << endl; cout << "k: " << (long)&k << endl; } ///:~ 

The result that I get:

 Address size 4 Long size 4 Intptr size 4 f(): 1 f(): 134514548 f(): 134514548 dog: 134521044 cat: 0x804a0d8 bird: 0x804a0dc fish: 134521056 i: -1074729380 i: -1074729380 j: -1074729384 k: -1074729388 

Answer 1

Not. Perhaps, if this is unlikely, pointers require more storage requirements than any integer. If there is an integer type that is suitable, then for it there will be std::intptr_t (and possibly also std::uintptr_t ) the typedef specified in <cstdint> (only for C ++ 11).

You can check for the presence of intptr_t at the preprocessor stage by checking for the macro definition INTPTR_MAX (or INTPTR_MIN ) after #include <cstdint> .

If you just want to print the pointer value using std::cout , then you can apply it to void* (not necessary for int* , but necessary for char* ) and use << directly without casting to an integer type.

Answer 2

You can use assert (or another type of check). Verification must be in the form

assert (sizeof (& var) <= sizeof (long));