How to decipher this? / Как это расшифровать?

Question

x-=-(++x)-x

I thought this is correct: x=x--(++x)-x //x=1--(2)-1=1+2-1=2
But if х=1 then answer is 5.
Why is it so?

Answer 1

The compiler can pick any reasonable order to execute so:
x=3;
x=x++;
x could be either 3 or 4 depending on which assignment wins. You can't know for sure because, even if it is 4 today, tomorrow it could be 3 as the compiler got modified.
x=1;
x=x--+++x;
x could be 0 to 4 depending on which order the x assignment happen. These statement are guanteed to be undefined behavor so should never be coded.