Changing constant value by pointer variable

Hi guys.
I'm wondering if it's possible that when I declare an constant value and I point to it by pointer variable (not constant pointer variable) ... is it legible and possible to change the value that Im pointing at?

I mean for example lets assume

Code:

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const int var=10

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so if I point to this value by integer pointer variable (not constant pointer) will the value that Im pointing at (the value var) change?


another question in the same context, if I have pointer variable which it's constant (i.e like

Code:

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int const *ptr

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) so I can't change the value that ptr is pointing at
by ptr pointer, but I can declare another pointer variable like int *ptr2 and let it points to the
same value and then I can change the value by ptr2 pointer .. right?
in other words

Code:

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int const *ptr

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is a constant regarding to ptr itself but I can declare another
pointer variable which it's not const and change the value that ptr pointing at by
the new pointer variable .. right?

Quote:

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Originally Posted by JohnnyOmari

so if I point to this value by integer pointer variable (not constant pointer) will the value that Im pointing at (the value var) change?

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I believe that you will get undefined behaviour. If you compile at a high enough warning level, your compiler should warn you about this though, and while you could suppress that warning with a cast, you'll then be taking responsibility for the potential undefined behaviour. Having said that, such casting does have its uses with legacy APIs that might not be const-correct.

Quote:

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Originally Posted by JohnnyOmari

but I can declare another pointer variable like int *ptr2 and let it points to the
same value and then I can change the value by ptr2 pointer .. right?

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Yes, assuming that what ptr2 points to isn't actually constant, otherwise you risk undefined behaviour. So, it is not advisable to do this: it would be better to change ptr2 to be a pointer to non-const instead, and if you cannot do so, then it is a good hint that perhaps what ptr2 points to might really be constant, so you should not attempt to bypass the const-ness.