Re: Non-const, L-value temporary
johnchx2@yahoo.com wrote:
#include <string>
using std::string;
string ReturnByValue(); /* Defined elsewhere */
int main()
{
const string &cr = ReturnByValue();
string &r = const_cast<string&>( cr );
r = "I've been manipulated!";
}
The code above exhibits undefined behavior. 8.5.3/5 indicates that
the compiler is allowed to introduce a temporary of type const string
and bind the reference cr to that object.
The above code *would* expose undefined behaviour, had the compiler
actually make such copy. No compiler does that, thus there is no UB.
There is only *potential* risk of thereof, similarly to following:
int main()
{
int a, b;
std::cin >> a >> b;
std::cout << a + b;
}
const_cast<int&>( static_cast<const int&>( int() ) ) = 5;
has undefined behavior under both the current and future rules: the
reference winds up bound to a temporary of "true" const type, and
modifying that object results in undefined behavior.
indeed
B.
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