Re: Non-const, L-value temporary
brok@rubikon.pl ("Bronek Kozicki") writes:
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.
That logic is flawed. UB is 100% related to what the standard says
and 100% independent of what any compiler actually does; there's
nothing an implementation can do that changes that (including
documenting the behavior). If a compiler does not create the copy,
that's simply the way the undefined behavior is expressed on that
implementation.
--
Dave Abrahams
Boost Consulting
www.boost-consulting.com
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