Re: Copy construction with inaccessible base class copy c-tor
On 1 Mrz., 13:59, "James Kanze" <james.ka...@gmail.com> wrote:
That's undefined behavior, not an error requiring a diagnostic.
Most implementations will only detect it when linking, and of
course, he never got that far.
That's an interesting position, I never realized that. Does that mean,
that essentially every C++ program more or less relies on this kind
of UB? Even the standard provides class definitions, where
some of the usual suspects (copy c'tor, assignment op)
are declared but not defined, e.g. (I take N2134 as reference):
20.5.14.2:
// 20.5.14.2.6, undefined operators:
template<class Function2> bool operator==(const function<Function2>&);
template<class Function2> bool operator!=(const function<Function2>&);
22.1.1.1.2:
facet(const facet&); // not defined
void operator=(const facet&); // not defined
22.1.1.1.3:
void operator=(const id&); // not defined
id(const id&); // not defined
27.4.4:
basic_ios(const basic_ios& ); // not defined
basic_ios& operator=(const basic_ios&); // not defined
27.6.1.1.2:
sentry(const sentry&); // not defined
sentry& operator=(const sentry&); // not defined
27.6.2.3:
sentry(const sentry&); // not defined
sentry& operator=(const sentry&); // not defined
Of course one can argue that the standard is allowed to demand
that and library writers have to ensure it's realization, but that
seems
somewhat unsatisfactory to me.
Is this one of the implicite rules or explicitely spoken out?
(I haven't searched yet)
Greetings,
Daniel
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