对于C中的以下代码段,它是未指定的行为,未定义的行为还是没有?

#include <stdio.h>
int f1(void);
int f2(void);
int f3(void);
int x=10;
int main()
{

    x+=f1()+f2()+f3()+f2();
    printf("%d",x);
    return 0;

}
int f1()
{
    int x=25;
    x++;
    return x;

}
int f2()
{
    static int x=50;
    x++;
    return x;

}

int f3()
{
    x*=10;
    return x;
}
 int f4()
{
    x=500;
    return 0;

}

According to me ,the order of evaluation for the expression x+=f1()+f2()+f3()+f2(); would be:- f1() will be called first followed by f2() followed by f3() because () are evaluated from left to right. But for x+= it depends on when the value of x is subsituted.If it is subsituted before any function call then 1 will be added and if it is executed after function call then 500 will be added.

如果在main()中有int x = 1的声明,它是否仍将是未定义/未指定的。