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libstdc++: Use constexpr-if in std::function for C++11 and C++14

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This allows removing the _Target_handler class template, because it's no
longer needed to prevent instantiating invalid specializations of
_Function_handler.

libstdc++-v3/ChangeLog:

	* include/bits/std_function.h (_Target_handler): Remove.
	(function::target): Use constexpr-if for C++11 and
	C++14, with diagnostic pragmas to suppress warnings.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
This commit is contained in:
Jonathan Wakely
2025-04-28 14:51:57 +01:00
committed by Jonathan Wakely
parent 42046a0f5d
commit 5b32ce7f7b
1 changed files with 9 additions and 22 deletions
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31
libstdc++-v3/include/bits/std_function.h
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@@ -135,13 +135,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _Functor*
_M_get_pointer(const _Any_data& __source) noexcept
{
if _GLIBCXX17_CONSTEXPR (__stored_locally)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
if constexpr (__stored_locally)
{
const _Functor& __f = __source._M_access<_Functor>();
return const_cast<_Functor*>(std::__addressof(__f));
}
else // have stored a pointer
return __source._M_access<_Functor*>();
#pragma GCC diagnostic pop
}
private:
@@ -312,21 +315,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return false; }
};
// Avoids instantiating ill-formed specializations of _Function_handler
// in std::function<_Signature>::target<_Functor>().
// e.g. _Function_handler<Sig, void()> and _Function_handler<Sig, void>
// would be ill-formed.
template<typename _Signature, typename _Functor,
bool __valid = is_object<_Functor>::value>
struct _Target_handler
: _Function_handler<_Signature, typename remove_cv<_Functor>::type>
{ };
template<typename _Signature, typename _Functor>
struct _Target_handler<_Signature, _Functor, false>
: _Function_handler<void, void>
{ };
/**
* @brief Polymorphic function wrapper.
* @ingroup functors
@@ -644,13 +632,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
const _Functor*
target() const noexcept
{
if _GLIBCXX17_CONSTEXPR (is_object<_Functor>::value)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
if constexpr (is_object<_Functor>::value)
{
// For C++11 and C++14 if-constexpr is not used above, so
// _Target_handler avoids ill-formed _Function_handler types.
using _Handler = _Target_handler<_Res(_ArgTypes...), _Functor>;
if (_M_manager == &_Handler::_M_manager
if (_M_manager == &_Handler<_Functor>::_M_manager
#if __cpp_rtti
|| (_M_manager && typeid(_Functor) == target_type())
#endif
@@ -661,6 +647,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return __ptr._M_access<const _Functor*>();
}
}
#pragma GCC diagnostic pop
return nullptr;
}
/// @}