Is the sizeof(some pointer) always equal to four?

Question

For example: sizeof(char*) returns 4. As does int*, long long*, everything that I\'ve tried. Are there any exceptions to this?

Answer 1

The guarantee you get is that sizeof(char) == 1. There are no other guarantees, including no guarantee that sizeof(int *) == sizeof(double *).

In practice, pointers will be size 2 on a 16-bit system (if you can find one), 4 on a 32-bit system, and 8 on a 64-bit system, but there's nothing to be gained in relying on a given size.

Answer 2

In addition to the 16/32/64 bit differences even odder things can occur.

There have been machines where sizeof(int *) will be one value, probably 4 but where sizeof(char *) is larger. Machines that naturally address words instead of bytes have to "augment" character pointers to specify what portion of the word you really want in order to properly implement the C/C++ standard.

This is now very unusual as hardware designers have learned the value of byte addressability.

Answer 3

From what I recall, it's based on the size of a memory address. So on a system with a 32-bit address scheme, sizeof will return 4, since that's 4 bytes.

Answer 4

Size of pointer and int is 2 bytes in Turbo C compiler on windows 32 bit machine.

So size of pointer is compiler specific. But generally most of the compilers are implemented to support 4 byte pointer variable in 32 bit and 8 byte pointer variable in 64 bit machine).

So size of pointer is not same in all machines.

Answer 5

In addition to what people have said about 64-bit (or whatever) systems, there are other kinds of pointer than pointer-to-object.

A pointer-to-member might be almost any size, depending how they're implemented by your compiler: they aren't necessarily even all the same size. Try a pointer-to-member of a POD class, and then a pointer-to-member inherited from one of the base classes of a class with multiple bases. What fun.