Re: [v3 PATCH] Make the default constructors of tuple and pair conditionally explicit.

[Ville Voutilainen <ville dot voutilainen at gmail dot com>]

On 2 November 2015 at 17:19, Paolo Carlini <paolo.carlini@oracle.com> wrote:
> Anyway, so far the only detail which makes me a little nervous is the
> following:
>
> +  template <typename _Tp>
> +    struct __is_implicitly_default_constructible
> +      : public integral_constant<bool,
> +                    (is_default_constructible<_Tp>::value
> +                    &&
> __is_implicitly_default_constructible_safe<_Tp>::value)>
>
>
> I think we want to use __and_ (note that there isn't a single logical && in
> the whole type_traits, outside macros).


Yep. New patch, tested on Linux-PPC64. Minor typo fixes for the
changelog. Ok for trunk?


2015-11-01  Ville Voutilainen  <ville.voutilainen@gmail.com>

    Make the default constructors of tuple and pair conditionally explicit.
    * include/std/type_traits (
    __do_is_implicitly_default_constructible_impl,
    __is_implicitly_default_constructible_impl,
    __is_implicitly_default_constructible_safe,
    __is_implicitly_default_constructible): New.
    * include/bits/stl_pair.h (pair::pair()): Use it.
    * include/std/tuple (tuple<_T1, _T2>::tuple): Use it.
    * include/std/tuple (_ImplicitlyDefaultConstructibleTuple): New.
    * include/std/tuple (tuple<_Types...>::tuple()): Use it.
    * testsuite/20_util/declval/requirements/1_neg.cc: Adjust.
    * testsuite/20_util/is_implicitly_default_constructible/requirements/explicit_instantiation.cc:
New.
    * testsuite/20_util/is_implicitly_default_constructible/requirements/typedefs.cc:
Likewise.
    * testsuite/20_util/is_implicitly_default_constructible/value.cc: Likewise.
    * testsuite/20_util/make_signed/requirements/typedefs_neg.cc: Adjust.
    * testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc: Likewise.
    * testsuite/20_util/pair/cons/explicit_construct.cc: Likewise.
    * testsuite/20_util/tuple/cons/explicit_construct.cc: Likewise.

Attachment: conditional-explicit-default-ctors-pair-tuple3.diff
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