i expect const_cast removes constness! , now points at which i have commented are the areas i have doubt on, i expect cout<<x to give 5Code:#include<iostream> using namespace std; int main() { const int x = 10; int *p=NULL; cout<<x; p = const_cast<int*>(&x); if(p) { *p = 5; if(p==&x) cout<<"same!"; // yes both point at same loc cout<<x; //gives 10 cout<<*p; //gives 5 } getchar(); return 0; }
However I also believe, how can i cast a const object to a non-const pointer!
Actually, this is undefined behaviour. Technically, your compiler can emit any code it wants to.
const cast isn't meant to remove constness on a const object, it's there to remove constness on a const pointer or reference to non-const object.
Code:int x = 0; const int y = 0; const int* cX = &x; const int* cy = &y; int *px = const_cast<int *>(cx); *px = 10; // ok, but you must KNOW that x is not const int *py = const_cast<int *>(cy); *py = 10; // arrghh, undefined behaviour!!
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Free Compiler: Visual C++ 2005 Express
If you program in C++, you need Boost. You should also know how to use the Standard Library (STL). Want to make games? After reading this, I don't like WxWidgets anymore.Want to add some scripting to your App?
thanx !
And to explain the particular behaviour of your implementation: since x is a constant and thus cannot be changed, the compiler simply replaces all uses of x by its constant value.
All the buzzt!
CornedBee
"There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
- Flon's Law
And to further clarify, the reason the language even allows you to do this is only because certain third party libraries are broken and take non-const parameters even when they are treated as const. const_cast<> is the only way to create a non-const pointer from a const pointer in order to pass data into these broken libraries.Originally Posted by ChaosEngine
If people could be counted on to properly const-ify their input parameters, const_cast<> would have no reason to exist.
Ah, but const_cast has another use. It can also be used to add or remove the volatile qualifier.
There is no greater sign that a computing technology is worthless than the association of the word "solution" with it.
True, but again, I'm not sure why you'd ever need to, if code is properly designed.
Adding volatile is an implicit cast. It's not necessary to use const_cast for it.
Removing it is nearly as dangerous as removing const.
All the buzzt!
"There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
- Flon's Law
