How to get Word length

stackoverflow How to determine processor word length in C?

A

As @holgac mentioned, the long datatype is always the same size as the machine's native word size:

"A word is the amount of data that a machine can process at one time." "The size of a processor’s general-purpose registers (GPRs) is equal to its word size." "Additionally, the size of the C type long is equal to the word size, whereas the size of the int type is sometimes less than that of the word size"

-- Linux Kernel Development, Ch 17 (3^rd edition, pg 381)

As indicated by Thomas Matthews however, this may not apply to machines with small word lengths.

To determine the size of long on your compiler, just use sizeof(long):

#include"stdio.h"
#include <limits.h>

int main(void)
{
    printf("long is %d bits on this system\n", (int) sizeof(long) * CHAR_BIT);
    return 0;
}

C program that get the architecture（32 or 64 bit )

void initServerConfig(void) {
    server.arch_bits = (sizeof(long) == 8) ? 64 : 32;
}

这段代码中使用的方法是从redis的server.c的initServerConfig函数中截取过来的，下面是测试程序:

#include<iostream>
int main()
{
    int arch_bits = (sizeof(long) == 8) ? 64 : 32;
    std::cout << arch_bits << std::endl;
}