如何使用结构指针访问结构成员

Question

I have following code:

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

struct tag
{
    int x;
};

int main()
{
    struct tag stvar;
    struct tag*stptr=&stvar;

    *(stptr).x=9;

    return 0;
}

I could use stptr->x but not *(stptr).x . I am getting request for member 'x' in 'stptr', which is of pointer type 'tag*' (maybe you meant to use '->' ?) Where am i getting it wrong? How to access member with struct pointers?

Answer 1

Change:

*(stptr).x=9;

to

(*stptr).x=9;

The first statement is equivalent to *(stptr.x)=9; as postfix operators have higher precedence than unary operators. Of course it is better to use the dedicated -> operator to write this statement:

stptr->x=9;

Answer 2

In general accessing structure variables can be gone in two ways

value.structure_variable; // using (.) operator

or

( address or pointer )-> structure_variable // using -> operator

as ouah pointed out in the answer

*(stptr).x=9;

is a wrong assignment, on the other hand

(*stptr) is basically the value at address pointer by stptr hence translates to a value thus

(*stptr).x=9; 

is Valid, also since stptr is a pointer itself

stptr->x = 9;

is harmless , safe and most popular way to assign.