C++ - An assignment not assigned

Question

Let's consider the following code:

int x = 10, s = 0;
s = sizeof(x = x + 20);
cout << x;

Result is always 10, irrespective what number you use instead of 20.
Is like assignment internal to sizeof() is not performed.
Why so?

Answer 1

Paolo De Nictolis sizeof () operator is return the size of the data types, as you have declare integers value which size is 4 so answer always become 4 which is default size of integer.
On printing the value of x always 10 will be coming as their is no operation performing outside the size of operator and inside the size of will return only the size of data type