Unexpected Result After Arithmetically Right Shifting

In the following code when I arithmetically right shift MSB3 (which happens to be 0) by 31 I get 2.

But when I replace MSB3 by 0 I get 0, which is the result I was expecting in the first case.

Why does this happen?

    const int value = 0;  //This happens after adding 0x80000000 to 0x80000000
    const int mask = 0x1;
    const int mask2 = mask << 31;
    const int MSB3 = value & mask2; // MSB3 = 0
    const int trueMSB3 = (MSB3 >> 31) // This gives 2 rather than 0???
    const int trueMSB3 = (0 >> 31) //Gives 0

If you have 64-bit ints then this is not possible as you have described it; since shifting 0 always gives 0. The "real code" must be different to what you have posted.

If you have 32-bit int then your program already caused undefined behaviour by doing mask << 31. Shifting into the sign bit causes UB. The result of this is that anything can happen; including subsequent code printing 2, or missiles being launched.

Your first comment indicates that maybe the "real code" did not have const int value = 0;, but some other code which you describe. It would be better to post the real code. That code may also have undefined behaviour, judging by your description.

To get well-defined results when doing shifts, use unsigned integers instead. To get better help, update your posted code to be a MCVE and include which compiler and system you are on.