非左值數組可以具有下標

 

#include <stdio.h>

struct line {
  int length;
  char contents[0];
};

struct line* get_struct_line(struct line *thisline)
{
    thisline = (struct line *)malloc(sizeof(struct line) + 10);
    thisline->length = 10;
    return thisline;
}

int main()
{

struct line * main_line = NULL;

   //get_struct_line(main_line);

    printf("length = %d/n",get_struct_line(main_line)->length); /* 非左值數組可以具有下標，一個函數的傳回值是一個結構體或是結構體指標的話，則可以直接使用"."或是"->"，得到結構體的子項目。 */
}

 

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liudan@liudan-desktop:/media/LIUDAN/aa/leftvalue_bracket$ gcc -o lvb generalized_lvalue.c
generalized_lvalue.c: In function ‘get_struct_line’:
generalized_lvalue.c:10: warning: incompatible implicit declaration of built-in function ‘malloc’
liudan@liudan-desktop:/media/LIUDAN/aa/leftvalue_bracket$ ./lvb
length = 10
liudan@liudan-desktop:/media/LIUDAN/aa/leftvalue_bracket$