On 27/08/21 00:13 +0100, Jonathan Wakely wrote:
This makes the std::function constructor use perfect forwarding, to
avoid an unnecessary move-construction of the target. This means we need
to rewrite the _Function_base::_Base_manager::_M_init_functor function
to use a forwarding reference, and so can reuse it for the clone
operation.
Also simplify the SFINAE constraints on the constructor, by combining
the !is_same_v<remove_cvref_t<F>, function> constraint into the
_Callable trait.
Signed-off-by: Jonathan Wakely <jwak...@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/std_function.h (_function_base::_Base_manager):
Replace _M_init_functor with a function template using a
forwarding reference, and a pair of _M_create function
templates. Reuse _M_create for the clone operation.
(function::_Decay_t): New alias template.
(function::_Callable): Simplify by using _Decay.
(function::function(F)): Change parameter to forwarding
reference, as per LWG 2447. Add noexcept-specifier. Simplify
constraints.
(function::operator=(F&&)): Add noexcept-specifier.
* testsuite/20_util/function/cons/lwg2774.cc: New test.
* testsuite/20_util/function/cons/noexcept.cc: New test.
This makes the new static_asserts give a slightly nicer error message
that doesn't involve <template-parameter-2-2>.
Tested powerpc64le-linux. Committed to trunk.
commit 952095bb053cfef47b48cc4345d658b8d8829800
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Fri Aug 27 00:20:31 2021
libstdc++: Name std::function template parameter
This avoids "<template-parameter-2-2>" being shown in the diagnostics
for ill-formed uses of std::function constructor:
In instantiation of 'std::function<_Res(_ArgTypes ...)>::function(_Functor&&)
[with _Functor = f(f()::_Z1fv.frame*)::<lambda()>;
<template-parameter-2-2> = void; _Res = void; _ArgTypes = {}]'
Instead we get:
In instantiation of 'std::function<_Res(_ArgTypes ...)>::function(_Functor&&)
[with _Functor = f(f()::_Z1fv.frame*)::<lambda()>;
_Constraints = void; _Res = void; _ArgTypes = {}]'
Signed-off-by: Jonathan Wakely <jwak...@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/std_function.h (function::function(F&&)): Give
name to defaulted template parameter, to improve diagnostics.
Use markdown for more doxygen comments.
diff --git a/libstdc++-v3/include/bits/std_function.h b/libstdc++-v3/include/bits/std_function.h
index 82c932e0db5..3dda820bd1a 100644
--- a/libstdc++-v3/include/bits/std_function.h
+++ b/libstdc++-v3/include/bits/std_function.h
@@ -326,10 +326,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ };
/**
- * @brief Primary class template for std::function.
+ * @brief Polymorphic function wrapper.
* @ingroup functors
- *
- * Polymorphic function wrapper.
+ * @since C++11
*/
template<typename _Res, typename... _ArgTypes>
class function<_Res(_ArgTypes...)>
@@ -364,7 +363,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* @brief Default construct creates an empty function call wrapper.
- * @post @c !(bool)*this
+ * @post `!(bool)*this`
*/
function() noexcept
: _Function_base() { }
@@ -379,10 +378,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* @brief %Function copy constructor.
* @param __x A %function object with identical call signature.
- * @post @c bool(*this) == bool(__x)
+ * @post `bool(*this) == bool(__x)`
*
- * The newly-created %function contains a copy of the target of @a
- * __x (if it has one).
+ * The newly-created %function contains a copy of the target of
+ * `__x` (if it has one).
*/
function(const function& __x)
: _Function_base()
@@ -399,7 +398,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @brief %Function move constructor.
* @param __x A %function object rvalue with identical call signature.
*
- * The newly-created %function contains the target of @a __x
+ * The newly-created %function contains the target of `__x`
* (if it has one).
*/
function(function&& __x) noexcept
@@ -418,22 +417,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @brief Builds a %function that targets a copy of the incoming
* function object.
* @param __f A %function object that is callable with parameters of
- * type @c T1, @c T2, ..., @c TN and returns a value convertible
- * to @c Res.
+ * type `ArgTypes...` and returns a value convertible to `Res`.
*
* The newly-created %function object will target a copy of
- * @a __f. If @a __f is @c reference_wrapper<F>, then this function
- * object will contain a reference to the function object @c
- * __f.get(). If @a __f is a NULL function pointer or NULL
- * pointer-to-member, the newly-created object will be empty.
+ * `__f`. If `__f` is `reference_wrapper<F>`, then this function
+ * object will contain a reference to the function object `__f.get()`.
+ * If `__f` is a null function pointer, null pointer-to-member, or
+ * empty `std::function`, the newly-created object will be empty.
*
- * If @a __f is a non-NULL function pointer or an object of type @c
- * reference_wrapper<F>, this function will not throw.
+ * If `__f` is a non-null function pointer or an object of type
+ * `reference_wrapper<F>`, this function will not throw.
*/
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 2774. std::function construction vs assignment
template<typename _Functor,
- typename = _Requires<_Callable<_Functor>>>
+ typename _Constraints = _Requires<_Callable<_Functor>>>
function(_Functor&& __f)
noexcept(_Handler<_Functor>::template _S_nothrow_init<_Functor>())
: _Function_base()
