[LC++]ambiguity, temporaries, const
9odb6x3rfr001 at sneakemail.com
Sun Jan 6 03:36:05 UTC 2002
Roberto Diaz roberto at vivaldi.dhis.org [mltuxcpp/linux-cpp list] wrote:
> The following code shows that under gcc 2.95
> * Theres not ambiguity in f(P&) and f(const P&)
It is supposed to work that way; it is useful to be able to
"overload on const" (and volatile) the same function. This means
void f(P &);
void f(P const &);
void f(P volatile &);
void f(P const volatile &);
are four separate functions.
> * Temporaries passed by reference default to const &
Not only this, attempting to pass a temporary to a function
taking P& (comment out the declaration of f(P const &) to see)
should result in a diagnostic. This is because generally this
is unexpected: the function would modify the temporary and
the result of such modifications would be lost as the
temporary is destroyed shortly thereafter.
> * Non-temporaries default to non-const
Actually, declared objects have the "cv-qualification" (an abbreviation
for "const or volatile qualification" which appears in the
declaration. Combine this:
P const cp;
P volatile vp;
P const volatile cvp;
with the four overloads of f() and see what happens. All of this
is in the C++ standard.
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