运算符优先级在C ++中的行为不正常

Question

Consider this code :

int func1()
{
    cout<<"Plus"<<endl;
    return 1;
}
int func2()
{
   cout<<"Multiplication"<<endl;
   return 2;
}
int main()
{
  cout<<func1()+4*func2();
}

According to this page * operator has higher precedence than + operator So I expect the result to be :

Multiplication 
Plus
9

But the result is

Plus 
Multipication
9

!! What is going on in compiler parser ?! Does compiler prefer Operator associaty ? Is the output same in all c/c++ compilers?

Answer 1

Operator precedence is not the same thing as order of evaluation.

You have no guarantee about the order of evaluation - the compiler is free to call functions in whatever order it likes within an expression so long as you get the correct result.

(A minor qualification: anything which introduces a sequence point (which includes short circuit operators), will have an effect on order of evaluation, but there are no sequence points within the expression in this particular case.)

Answer 2

The compiler is free to evaluate functions in any order it pleases - the only cases within expressions where the order of evaluation is guaranteed are the sequence points; operators || , && , , , and ? of the ternary conditional operator ? : ? : are sequence points. In each case the left side has all its values and side effects evaluated before the right side is touched.