sizeof, strlen实例比较

test_sizeof.c

#include<stdio.h>
#include<string.h>

void testfun(char p[])            //这里会隐式转化成char*p
{
  printf("sizeof(p) is %u\n",sizeof(p));
  printf("strlen(p) is %u\n",strlen(p));
}


int main()
{
  char *p1="hello world1";     //vi  test_sizeof时只有这个！而hello world2不在二进制文件中，因为其空间不是在.rodata里分配的。
  char p2[]="hello world2";
  char p3[]={'h','e','l','l','o',' ','w','o','r','l','d','3'};
  printf("sizeof(p1) is %u\n",sizeof(p1) );  //sizeof是运算符，不在任何头文件中！
  printf("sizeof(p2) is %u\n",sizeof(p2) );
  printf("sizeof(p3) is %u\n",sizeof(p3) );
  printf("strlen(p1) is %u\n",strlen(p1) );
  printf("strlen(p2) is %u\n",strlen(p2) );
  printf("strlen(p3) is %u\n",strlen(p3) );

  printf("---------------------------------------------------\n");
  testfun(p1);
  printf("---------------------------------------------------\n");
  testfun(p2);
  printf("---------------------------------------------------\n");
  testfun(p3);


}
结果：
sizeof(p1) is 4
sizeof(p2) is 13
sizeof(p3) is 12
strlen(p1) is 12
strlen(p2) is 12
strlen(p3) is 12

---------------------------------------------------
sizeof(p) is 4
strlen(p) is 12
---------------------------------------------------
sizeof(p) is 4
strlen(p) is 12
---------------------------------------------------
sizeof(p) is 4
strlen(p) is 12