delete cout; delete cin; do not give compilation error - a flaw in the Standard library?

Question

Will the following give a compilation error?

delete cout;
delete cin;

The answer is : No.

It is a flaw in the implementation of strea

Answer 1

It has apparently been fixed.

At least, in N3290 you have std::basic_ios::operator bool instead of that void* conversion, and this operator bool is declared explicit.

Note that C++98/C++03 did not support explicit type conversion operators, but C++11 does.

An explicit type conversion operator

N3290 §12.3.2/2;
is only considered as a user-defined conversion for direct-initialization (8.5)

And that might seem to be impractical for the condition in e.g. a while or for statement.

Happily,

N3290 §4/3;
An expression e can be implicitly converted to a type T if and only if the declaration T t=e; is well-formed, for some invented temporary variable t (8.5). Certain language constructs require that an expression be converted to a Boolean value. An expression e appearing in such a context is said to be contextually converted to bool and is well-formed if and only if the declaration bool t(e); is well-formed, for some invented temporary variable t (8.5). The effect of either implicit conversion is the same as performing the declaration and initialization and then using the temporary variable as the result of the conversion.

where bool t(e); is a direct-initialization.

E.g. you don’t have to explicit convert a stream object used as condition in a while, because there is implicitly an explicit conversion (he he).

Unfortunately, searching N3290 I can’t find any list of the “certain language constructs” where this happens, but in comments to this answer JohannesD wrote:

Searched through the FDIS for “contextually”, and the whole list seems to be: if, while, do, for, noexcept, and static_assert conditions; the first operand of ?:; both operands of && and ||; and the operand of !.

Cheers & hth.,