Re: [PATCH 1/4] media: si2168: use bits instead of bool for flags

From: Gon Solo
Date: Thu Oct 10 2019 - 06:55:51 EST

On Fri, Oct 04, 2019 at 10:15:22AM -0300, Mauro Carvalho Chehab wrote:
> Using bool on struct is not recommended, as it wastes lots of
> space. So, instead, let's use bits.

Wouldn't "bool b:1;" even be better? I performed a little test:

#include <stdbool.h>
#include <stdio.h>

struct uints {
unsigned int a0;
unsigned int a1;
unsigned int a2;
unsigned int a3;
unsigned int a4;
unsigned int a5;
unsigned int a6;
unsigned int a7;

struct bools {
bool a0;
bool a1;
bool a2;
bool a3;
bool a4;
bool a5;
bool a6;
bool a7;

struct bit_uints {
unsigned int a0:1;
unsigned int a1:1;
unsigned int a2:1;
unsigned int a3:1;
unsigned int a4:1;
unsigned int a5:1;
unsigned int a6:1;
unsigned int a7:1;

struct bit_bools {
bool a0:1;
bool a1:1;
bool a2:1;
bool a3:1;
bool a4:1;
bool a5:1;
bool a6:1;
bool a7:1;

int main() {
printf("bit_uints: %ld\n", sizeof(struct bit_uints));
printf("bit_bools: %ld\n", sizeof(struct bit_bools));
printf("uints: %ld\n", sizeof(struct uints));
printf("bools: %ld\n", sizeof(struct bools));


bit_uints: 4
bit_bools: 1
uints: 32
bools: 8

I know with different types within the struct it looks different, but