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);. Function should handle each n from 0 to 32.
Especially value n==32 should be handled.
If you meant the least-significant n bits:
((uint32_t)1 << n) - 1
On most architectures, this won't work if n is 32, so you may have to make a special case for that:
n == 32 ? 0xffffffff : (1 << n) - 1
On a 64-bit architecture, a (probably) faster solution is to cast up then down:
(uint32_t)(((uint64_t)1 << n) - 1)
In fact, this might even be faster on a 32-bit architecture since it avoids branching.