C: storing string which is more efficient.

tuxdev · 08-31-2006, 07:22 PM

the size of int and int* are not always the same. In x86_64 systems, int is 4 bytes but int* is 8 bytes.

debiant · 08-31-2006, 07:31 PM

Quote:

Originally Posted by tuxdev

the size of int and int* are not always the same. In x86_64 systems, int is 4 bytes but int* is 8 bytes.

In this instance would you want to cast the pointer then or is that why it is dangerous?

Or more appropriately p = malloc(sizeof(int)); will send a 4 byte address to p to store, what about the other 4?

jlliagre · 08-31-2006, 07:48 PM

Quote:

Originally Posted by debiant

In this instance would you want to cast the pointer then or is that why it is dangerous?

Or more appropriately p = malloc(sizeof(int)); will send a 4 byte address to p to store

A 8 bytes address actually, if this a 64 bit CPU.

Quote:

what about the other 4?

They do not exist.

tuxdev · 08-31-2006, 07:51 PM

The size of pointers vs primitives isn't the reason not to cast. The cast shuts up the compiler in -Wall mode so it can't complain that malloc doesn't exist yet. In C++ OTOH, the cast is required, but that doesn't matter here.

debiant · 08-31-2006, 08:26 PM

Quote:

Originally Posted by jlliagre

A 8 bytes address actually, if this a 64 bit CPU.

They do not exist.

What is the point of a 64 bit address for a 32 bit integer?

jlliagre · 08-31-2006, 08:38 PM

Well, you can have 4 billions times more.

Also: what is a point of a 32 bit address for a 8 bit byte ?

debiant · 09-01-2006, 12:24 AM

I'll study up because I don't seem to comprehend storing a 16 bit or 32 bit value in a 64 bit address.

xhi · 09-01-2006, 12:39 AM

Quote:

Originally Posted by debiant

I'll study up because I don't seem to comprehend storing a 16 bit or 32 bit value in a 64 bit address.

when you are talking about a pointer you are not storing a 16 or 32 bit value in a 64 bit address, you are storing the address of a memory location that holds the 16 or 32 bit value.

the actual memory location that is holding the data is still at the size of the type. but any ptrs that would point to that location are the size of a ptr, which is sized to address the entire address space, which is 64 bit.