Using in user programs, or in driver module code…does it matter?

Question

I\'m developing a device driver module and associated user libraries to handle the ioctl() calls. The library takes the pertinent info and puts it into a struc

Answer 1

Fixed length integers in the Linux kernel

The Linux kernel already has fixed length integers which might interest you. In v4.9 under include/asm-generic/int-ll64.h:

typedef signed char s8;
typedef unsigned char u8;

typedef signed short s16;
typedef unsigned short u16;

typedef signed int s32;
typedef unsigned int u32;

typedef signed long long s64;
typedef unsigned long long u64;

LDD3 has a chapter about data sizes as well: https://static.lwn.net/images/pdf/LDD3/ch11.pdf

LDD3 mentions there that the best printk strategy is to cast to just cast to the largest integer possible with correct signedness: %lld or %llu. %ju appears unavailable under the printk formatting centerpiece lib/linux/vsprintf.c.