why is u8 u16 u32 u64 used instead of unsigned int in kernel programming
Adding my 10 cents to this answer:
u64
means an 'unsigned 64 bits' value, so, depending on the architecture where the code will run/be compiled, it must be defined differently in order to really be 64 bits long.
For instance, on a x86 machine, an unsigned long
is 64 bits long, so u64
for that machine could be defined as follows:
typedef unsigned long u64;
The same applies for u32
. On a x86 machine, unsigned int
is 32 bits long, so u32
for that machine could be defined as follows:
typedef unsigned int u32;
You'll generally find the typedef
declaration for these types on a types.h
file which corresponds to the architecture you're compiling your source to.
Often when working close to the hardware or when trying to control the size/format of a data structure you need to have precise control of the size of your integers.
As for u8
vs uint8_t
, this is simply because Linux predated <stdint.h>
being available in C, which is technically a C99-ism, but in my experience is available on most modern compilers even in their ANSI-C / C89 modes.