列印c語言整型記憶體表示

錯誤版本

#include <stdio.h>void show_bytes(const  char * a, unsigned len){    int i;    for( i=0; i<len; i++)        printf("%.2x",*(a+i));    printf("\n");}int main(void){    short x = 12345;    short mx = -x;    show_bytes(( char *) &x, sizeof(x));    show_bytes(( char *) &mx, sizeof(short));    return 0;}

因為*(a+i)傳遞給printf時進行整型提升，而當有符號數進行整型提升時高位填充符號位。所以列印x正確，而列印mx錯誤

正確版本

#include <stdio.h>void show_bytes(const unsigned char * a, unsigned len){    int i;    for( i=0; i<len; i++)        printf("%.2x",*(a+i));    printf("\n");}int main(void){    short x = 12345;    short mx = -x;    show_bytes((unsigned char *) &x, sizeof(x));    show_bytes((unsigned char *) &mx, sizeof(short));    return 0;}