在带有stm32(arm cortex)CPU的IAR IDE中,我在原始情况下有非常奇怪的行为.
uint32_t s = 6654; //=0x000019FE
//next I'll see in IAR debugger
uint8_t res1 = 0;
res1 = (s&0xFF000000)>>24; //see in debugger: res1=00
res1 = (s&0x00FF0000)>>16; //res1=00
res1 = (s&0x0000FF00)>>8; //res1=19
res1 = (s&0x000000FF); //res1=FE
void *sp = &s;
uint8_t res2 = 0;
res2 = *((uint8_t*)sp+0); //res2=FE but must be 00!
res2 = *((uint8_t*)sp+1); //res2=19 but must be 00!
res2 = *((uint8_t*)sp+2); //res2=00 but must be 19!
res2 = *((uint8_t*)sp+3); //res2=00 but must be FE!
(请参阅我期望的评论,以及会发生什么.)为什么我得到这个结果？我没有解释.