How can a value of a constant be varied through a pointer ?

[Adam D. Ruppe via Digitalmars-d-learn]

On Sunday, 20 September 2015 at 00:09:52 UTC, RADHA GOGIA wrote:
> I went through these two links and found that this behaviour is 
> undefined , but the only issue which I have is that in one 
> sense we say that since local variables live on stack , hence 
> they cannot be located on read only memory region but if this 
> is so then if I try to alter the value of the constant directly 
> through assignment then why does it show error if it is not 
> located in the read only memory region :


const in C (and D) isn't necessarily related to read-only memory 
on the hardware level. It is a feature of the type system - 
because the VARIABLE is marked const, the compiler will complain 
if you try to write to it.


> const int a=12;
> int *ptr ;
> ptr=&a;
> *ptr=8; // no error

BTW, that is allowed in C, but would be a compile error in D - 
D's type system propagates the const to pointers too.