Puzzle on C/C++ R-Value expression?

Here we will see a puzzle. Suppose there is a program like below, we have to tell what is output and why?

Example

#include using namespace std; int main() { int x = 0xab; ~x; cout << hex << x; }

So what is the output? ~x is performing a complement operation. So does it display the two's complement result in hex?

The output is as follows

Output

ab

So, there is no change. but why? The reason is that ~x is converting x to its complement form, but the value is not assigned to any variable. This expression is an R-value expression. The lvalue is not stored into some variable until it is used. If we enter the L value it will look like this -

Example

#include using namespace std; int main() { int x = 0xab; x = ~x; cout << hex << x; }

Output

ffffff54

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