What should be the sizeof(int) on a 64-bit machine? [duplicate]
Possible Duplicate:
size of int, long, etc
Does the size of an int depend on the compiler and/or processor?
What decides the sizeof an integer?
I'm using a 64-bit
machine.
$ uname -m
x86_64
$ file /usr/bin/file
/usr/bin/file: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, stripped
$
When I ran the following program, I got the sizeof(int)
as 4-bytes
.
#include <stdio.h>
int main(void)
{
printf("sizeof(int) = %d bytes\n", (int) sizeof(int));
return 0;
}
If I'm running a 16-
, 32-
and 64-
bit machine, then doesn't it mean that the size of an integer
is 16-
, 32-
and 64-
bit respectively?
In my machine, I found the WORD_BIT
is 32
. Shouldn't it be 64
on a 64-bit
machine?
$ getconf WORD_BIT
32
$
And, shouldn't the sizeof(int)
be 64-bits
(8 bytes
) in the above case?
Solution 1:
Size of a pointer should be 8 byte on any 64-bit C/C++ compiler, but not necessarily size of int.
Solution 2:
Doesn't have to be; "64-bit machine" can mean many things, but typically means that the CPU has registers that big. The sizeof a type is determined by the compiler, which doesn't have to have anything to do with the actual hardware (though it typically does); in fact, different compilers on the same machine can have different values for these.
Solution 3:
Not really. for backward compatibility it is 32 bits.
If you want 64 bits you have long
, size_t
or int64_t
Solution 4:
In C++, the size of int
isn't specified explicitly. It just tells you that it must be at least the size of short int
, which must be at least as large as signed char
. The size of char
in bits isn't specified explicitly either, although sizeof(char) is defined to be 1. If you want a 64 bit int, C++11 specifies long long
to be at least 64 bits.