c,variables,constants , Is there any way of protecting a variable for being modified at runtime in C?


Is there any way of protecting a variable for being modified at runtime in C?

Question:

Tag: c,variables,constants

I was wondering if there is any way of protecting a variable for being modified once initialized (something like "constantize" a variable at runtime ). For example:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    int v, op;
    scanf( "%d", &op );
    if( op == 0 )
        v = 1;
    else
        v = 2;
// here transform v to a constant...
    .
    .
// ...and that any attempt to modify v yields to an error.
    .
    .
    return EXIT_SUCCESS;
}

Answer:

You can make the result of the input be const like this:

int func()
{
    int op = 0;
    scanf( "%d", &op );
    if( op == 0 )
        return 1;
    else
        return 2;
}

int main()
{
    const int v = func();
    // ...
}

NB. Of course, there is no way to prevent undefined behaviour happening later in the program which appears to change v (since undefined behaviour can, by definition, have any effect).


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