Strange c++ pointer behavior.

Question

Can anyone explain me what is happening in this code?
https://code.sololearn.com/cV9D58KF6g7Z/?ref=app

Answer 1

The code is mixing up "compile time' and "runtime" assumptions.

When your code is compiled, the compiler (in this case!) is tracking constants (err, ro-values) and substituting their values into the final executable.

What you're doing is undefined/compiler-specific/should throw a warning / discard 'const', etc

See the explanations here:
https://stackoverflow.com/questions/15576000/in-c-can-a-const-variable-be-modified-via-a-pointer

[inside the compiler]
Here's the assembly for your code. It has never run, so you are seeing "compile-time" decisions. You can see that the compiler believes 'a' is supposed to have its original value so it substitutes it into the assembly (no runtime memory is involved!):
https://godbolt.org/z/DAcdgx

Answer 2

// Hi Ali Hoo,
In the line 6, you use "const" to create a variable.

But if you use const, the value cannot be modified.

Correction : delete "const" in the line 6

Answer 3

Thank you. But my compiler (vs 2017) didn't show any warning. My executable work fine and shows the same output. I changed const with constexpr but I got the same answer.