c语言常见错误

#include <stdio.h>

#include <stdlib.h>

int main(void)

{

unsigned long l1 = 0xffffffff;

int *j, *k, i = 2;

// *k = 4; 错误用法，只为指针分配了空间， 还没为内存指向分配空间， 程序将core dump.

k = malloc(sizeof(int));;

j = malloc(sizeof(int));;

*k = 4;

// free(k);

free(j);

j = k, k = &i;

// k = &i;

printf("test j:%d,k:%d\n", *j, *k);

/*

if (l1 = ~0U)

printf("test1:%lu,%d\n", l1, l1);

else

printf("not equal test1:%lu,%d\n", l1, l1);

printf("test, int:%d, unsigned int:%d, unsigned long:%d\n", sizeof(int), sizeof(unsigned int), sizeof(unsigned long long));

*/

return 0;

}