The compiler should emit a warning that an integer conversion resulted in truncation when assigning an integer constant to a bit-field that is too small to hold the integer value. The compiler does not emit a warning when the declared type of the bit-field is big enough to hold the integer value, even though the actual bit-field might be too small to represent the value.

#include <stdint.h>

struct
{
    uint32_t hi:16;
    uint32_t lo:16;
} s;

void foo()
{
    uint16_t l  = 0x10000U;
    s.lo = 0x10000U; /* should get the same warning, but doesn't */
}