Is const_cast safe?
c++, casting, const-cast
Solution
`const_cast` is safe only if you're casting a variable that was originally non-`const`. For example, if you have a function that takes a parameter of a `const char *`, and you pass in a modifiable `char *`, it's safe to `const_cast` that parameter back to a `char *` and modify it. However, if the original variable was in fact `const`, then using `const_cast` will result in undefined behavior.
void func(const char *param, size_t sz, bool modify)
{
if(modify)
strncpy(const_cast<char *>(param), sz, "new string");
printf("param: %s\n", param);
}
...
char buffer[16];
const char *unmodifiable = "string constant";
func(buffer, sizeof(buffer), true); // OK
func(unmodifiable, strlen(unmodifiable), false); // OK
func(unmodifiable, strlen(unmodifiable), true); // UNDEFINED BEHAVIOR
Problem
I can't find much information on `const_cast`. The only info I could find (on Stack Overflow) is: The `const_cast<>()` is used to add/remove const(ness) (or volatile-ness) of a variable. This makes me nervous. Could using a `const_cast` cause unexpected behavior? If so, what? Alternatively, when is it okay to use `const_cast`?