CODEWITHSUNDEEP
cbit-fields
sobin thomas
sobin thomas

Reputation: 59

How the elements are stored in bit-field

Recently i faced a problem with bit fields

union u
{
    struct
    {
        unsigned char x : 2;
        unsigned int y : 2;
    }p;
    int x;
};
int main()
{
    union u u = { 2 };
    printf("%d\n", u.p.x);
}

Its printing 2 actually as per the little endian rule. bitfield y should be assigned 2 why 2 is assigned to x

Upvotes: 2

Views: 44

Answers (1)

pero_hero
pero_hero

Reputation: 3204

When using

union u u = { 2 };

you are actaully assigning the member u.p.x as it is the first member of struct p according to

When initializing a union, the initializer list must have only one member, which initializes the first member of the union unless a designated initializer is used (since C99). cppreference

if you want initialize u.p.y use:

union u u =  { {.y = 2} };

or

union u ux = { .p={ 0,2 } };

Upvotes: 1

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