#include int main(int argc, char * argv[])
{
printf("int 长度为 ：%ld\n", sizeof(int));
int *p, b = 1;
int nbytes;
//测试本机64位机,只要参数小于24(包括0)
//第一次最小分配24字节
//若大于24字节, 例如1000,则分配1000或者1000大一点内存
p = (int *)malloc(0);
if(p == NULL)
{
perror("malloc");
exit(1);
}
nbytes = malloc_usable_size(p);
printf("动态内存的长度为：%d\n", nbytes);
printf("a的长度:%ld\n", sizeof(p)); //指针:32位4字节,64位8字节
p[0] = 1;
p[1] = 2;
p[2] = 3;
p[3] = 4;
p[4] = 4;
p[5] = 5;
//p[6] = 6; //当超出分配的空间24,程序崩溃(必须有free, 设置NULL则是个良好的习惯)
printf("b = %d\n", b);
printf("p = %d\n", *p);
printf("指针地址：b - %p\n", &b);
printf("释放前，指针地址：a - %p\n", p);
free(p);
p = NULL;
printf("释放后，指针地址：a - %p\n", p);
if(p != NULL)
printf("p = %d\n", *p);
else
printf("p is NULL, %p \n", p);
return 0;
}