Set last `n` bits in unsigned int

Question

How to set (in most elegant way) exactly n least significant bits of uint32_t? That is to write a function void setbits(uint32_t *x, int n);<

Answer 1

If n is zero then no bits should be set based on the question.

const uint32_t masks[32] = {0x1, 0x3, 0x7, ..., 0xFFFFFFFF};

void setbits(uint32_t *x, int n)
{
    if ( (n > 0) && (n <= 32) )
    {
        *x |= masks[--n];
    }
}