this is a gcc file, you can download it and learn its usetility, for further detail please look at t
源代码在线查看: f-2-25-27.c
#include struct sss{ int i1:2; int i2:25; int i3:27; }; static union u{ struct sss sss; unsigned char a[sizeof (struct sss)]; } u; int main (void) { int i; for (i = 0; i < sizeof (struct sss); i++) u.a[i] = 0; u.sss.i1 = 3.0; for (i = 0; i < sizeof (struct sss); i++) printf ("%x ", u.a[i]); printf ("\n"); u.sss.i2 = 33554431.0; for (i = 0; i < sizeof (struct sss); i++) printf ("%x ", u.a[i]); printf ("\n"); u.sss.i3 = 134217727.0; for (i = 0; i < sizeof (struct sss); i++) printf ("%x ", u.a[i]); printf ("\n"); return 0; }