Avoid creating arbitrarily large objects on the stack when emplacing
trivially copyable objects into a variant. Currently we provide the
strong exception-safety guarantee for all trivially copyable types, by
constructing a second variant and then doing a non-throwing move
assignment from the temporary. This patch restricts that behaviour to
trivially copyable types that are no larger than 256 bytes. For larger
types the object will be emplaced directly into the variant, and if its
initialization throws then the variant becomes valueless.
Also implement Antony Polukhin's suggestion to whitelist specific types
that are not trivially copyable but can be efficiently move-assigned.
Emplacing those types will never cause a variant to become valueless.
The whitelisted types are: std::shared_ptr, std::weak_ptr,
std::unique_ptr, std::function, and std::any. Additionally,
std::basic_string, std::vector, and __gnu_debug::vector are whitelisted
if their allocator traits give them a non-throwing move assignment
operator. Specifically, this means std::string is whitelisted, but
std::pmr::string is not.
As part of this patch, additional if-constexpr branches are added for
the cases where the initialization is known to be non-throwing (so the
overhead of the try-catch block can be avoided) and where a scalar is
being produced by a potentially-throwing conversion operator (so that
the overhead of constructing and move-assigning a variant is avoided).
These changes should have no semantic effect, just better codegen.
PR libstdc++/87431 (again)
* include/bits/basic_string.h (__variant::_Never_valueless_alt):
Define partial specialization for basic_string.
* include/bits/shared_ptr.h (_Never_valueless_alt): Likewise for
shared_ptr and weak_ptr.
* include/bits/std_function.h (_Never_valueless_alt): Likewise for
function.
* include/bits/stl_vector.h (_Never_valueless_alt): Likewise for
vector.
* include/bits/unique_ptr.h (_Never_valueless_alt): Likewise for
unique_ptr.
* include/debug/vector (_Never_valueless_alt): Likewise for debug
vector.
* include/std/any (_Never_valueless_alt): Define explicit
specialization for any.
* include/std/variant (_Never_valueless_alt): Define primary template.
(__never_valueless): Use _Never_valueless_alt instead of
is_trivially_copyable.
(variant::emplace<N>(Args&&...)): Add special case for non-throwing
initializations to avoid try-catch overhead. Add special case for
scalars produced by potentially-throwing conversions. Use
_Never_valueless_alt instead of is_trivially_copyable for the
remaining strong exception-safety cases.
(variant::emplace<N>(initializer_list<U>, Args&&...)): Likewise.
* testsuite/20_util/variant/87431.cc: Run both test functions.
* testsuite/20_util/variant/exception_safety.cc: New test.
* testsuite/20_util/variant/run.cc: Use pmr::string instead of string,
so the variant becomes valueless.
From-SVN: r270170
The old version of _Sp_counted_ptr_inplace::_M_get_deleter (up to GCC
8.2.0) expects to be passed a real std::typeinfo object, so mixing that
with the new definition of the __shared_ptr constructor (which always
passes the fake tag) leads to accessing the fake object as a real
std::typeinfo. Instead of trying to make it safe to mix the old and new
definitions, just stop using that function. By passing a reference to
__shared_ptr::_M_ptr to the __shared_count constructor it can be set
directly, without needing to obtain the pointer via the _M_get_deleter
back-channel. This avoids a virtual dispatch (which fixes PR 87514).
This means that code built against new libstdc++ headers doesn't use
_M_get_deleter at all, and so make_shared works the same whether RTTI is
enabled or not.
Also change _M_get_deleter so that it checks for a real type_info object
even when RTTI is disabled, by calling a library function. Unless
libstdc++ itself is built without RTTI that library function will be
able to test if it's the right type_info. This means the new definition
of _M_get_deleter can handle both the fake type_info tag and a real
type_info object, even if built without RTTI.
If linking to objects built against older versions of libstdc++ then if
all objects use -frtti or all use -fno-rtti, then the caller of
_M_get_deleter and the definition of _M_get_deleter will be consistent
and it will work. If mixing -frtti with -fno-rtti it can still fail if
the linker picks an old definition of _M_get_deleter and an old
__shared_ptr constructor that are incompatible. In that some or all
objects might need to be recompiled.
PR libstdc++/87514
PR libstdc++/87520
PR libstdc++/88782
* config/abi/pre/gnu.ver (GLIBCXX_3.4.26): Export new symbol.
* include/bits/shared_ptr.h
(shared_ptr(_Sp_make_shared_tag, const Alloc&, Args&&...))
(allocate_shared): Change to use new tag type.
* include/bits/shared_ptr_base.h (_Sp_make_shared_tag::_S_eq):
Declare new member function.
(_Sp_alloc_shared_tag): Define new type.
(_Sp_counted_ptr_inplace): Declare __shared_count<_Lp> as a friend.
(_Sp_counted_ptr_inplace::_M_get_deleter) [!__cpp_rtti]: Use
_Sp_make_shared_tag::_S_eq to check type_info.
(__shared_count(Ptr, Deleter),__shared_count(Ptr, Deleter, Alloc)):
Constrain to prevent being called with _Sp_alloc_shared_tag.
(__shared_count(_Sp_make_shared_tag, const _Alloc&, Args&&...)):
Replace constructor with ...
(__shared_count(Tp*&, _Sp_alloc_shared_tag<_Alloc>, Args&&...)): Use
reference parameter so address of the new object can be returned to
the caller. Obtain the allocator from the tag type.
(__shared_ptr(_Sp_make_shared_tag, const Alloc&, Args&&...)): Replace
constructor with ...
(__shared_ptr(_Sp_alloc_shared_tag<Alloc>, Args&&...)): Pass _M_ptr
to the __shared_count constructor.
(__allocate_shared): Change to use new tag type.
* src/c++11/shared_ptr.cc (_Sp_make_shared_tag::_S_eq): Define.
From-SVN: r268086
PR libstdc++/88738
Warn about unused comparisons of shared_ptr/unique_ptr
* include/bits/c++config [_GLIBCXX_NODISCARD]: Define.
* include/bits/shared_ptr.h: Use it for operator ==, !=,
<, <=, >, >= for shared_ptr.
* include/bits/unique_ptr.h: Likewise for unique_ptr.
From-SVN: r267964
The standard doesn't specify this partial specialization (it was
required after the changes in N2637 but then should have been removed
following LWG 1262). Its presence is observable because it causes
different results when operator< has been overloaded for a shared_ptr
specialization.
PR libstdc++/86537
* include/bits/shared_ptr.h (less<shared_ptr<_Tp>>): Remove
non-standard partial specialization.
* include/bits/shared_ptr_base.h (_Sp_less): Remove class definition.
(less<__shared_ptr<_Tp, _Lp>): Remove partial specialization.
* testsuite/20_util/shared_ptr/comparison/86537.cc: New test.
From-SVN: r262739
* doc/xml/manual/status_cxx2017.xml: Update status.
* doc/html/manual/status.html: Regenerate.
* include/bits/shared_ptr.h (shared_ptr(unique_ptr<_Yp, _Del>)): Add
extension constructor to maintain C++14 behaviour.
* include/bits/shared_ptr_base.h (__sp_array_delete): Add new struct.
(__shared_count(_Ptr, false_type), __shared_count(_Ptr, true_type)):
New constructors.
(__sp_compatible_with, __sp_is_constructible): Add specializations
for array support.
(__sp_is_constructible_arr, __sp_is_constructible_arrN): New helpers.
(__shared_ptr_access): New base class for observer member functions.
(__shared_ptr::element_type): Use remove_extent.
(__shared_ptr::_UniqCompatible): Add __sp_compatible_with check.
(__shared_ptr(_Yp*)): Use tag dispatching to call new __shared_count
constructor.
(__shared_ptr(unique_ptr<_Yp, _Del>)): Add extension constructor.
(__shared_ptr::operator*, __shared_ptr::operator->): Remove and
inherit from __shared_ptr_access base class.
(__shared_ptr::__has_esft_base): Return false for array types.
(__weak_ptr::element_type): Use remove_extent.
* include/experimental/bits/shared_ptr.h (__libfund_v1): Remove.
(__shared_ptr<__libfund_v1<_Tp>>): Remove specializations.
(__wak_ptr<__libfund_v1<_Tp>>): Likewise.
(experimental::__sp_compatible_v): Redefine using
__sp_compatible_with.
(experimental::__sp_is_constructible_v): Redefine using
__sp_is_constructible.
(get_deleter, operator<<): Change argument from __shared_ptr to
shared_ptr.
* testsuite/20_util/shared_ptr/cons/array.cc: New test.
* testsuite/20_util/shared_ptr/cons/unique_ptr_array.cc: Adjust for
new behaviour.
* testsuite/20_util/shared_ptr/observers/array.cc: Test observers for
arrays.
* testsuite/20_util/shared_ptr/observers/array_neg.cc: New test.
From-SVN: r242369
* include/backward/auto_ptr.h (__shared_ptr(auto_ptr&&))
(shared_ptr(auto_ptr&&)): Adjust template parameter lists.
* include/bits/shared_ptr.h (__sp_compatible_with)
(__sp_is_constructible): New helper traits for shared_ptr.
(shared_ptr::_Convertible): Replace with _Constructible.
(shared_ptr::_Constructible, shared_ptr::_Assignable): Forward checks
to base class.
(shared_ptr::shared_ptr, shared_ptr::operator=): Constrain template
with _Constructible and _Assignable.
(shared_ptr::shared_ptr(shared_ptr<_Tp1>, _Tp*)): Use element_type
instead of _Tp.
(operator<): Likewise.
(operator>): Define in terms of operator<.
(static_pointer_cast, const_pointer_cast, dynamic_pointer_cast): Use
element_type instead of _Tp.
(reinterpret_pointer_cast): Define for C++17.
(weak_ptr::_Convertible): Replace with _Constructible.
(weak_ptr::_Constructible, weak_ptr::_Assignable): Forward checks
to base class.
(weak_ptr::weak_ptr, weak_ptr::operator=): Constrain templates
with _Constructible and _Assignable.
* include/bits/shared_ptr_base.h (__shared_ptr::_Convertible): Replace
with _Compatible.
(__shared_ptr::_SafeConv): New constraint for incoming raw pointers.
(__shared_ptr::_Compatible): New constraint for converting from
other types of shared_ptr and weak_ptr.
(__shared_ptr::_Assignable): Define in terms of _Compatible.
(__shared_ptr::_UniqCompatible, __shared_ptr::_UniqAssignable): New
constraints for converting from unique_ptr.
(__shared_ptr::__shared_ptr, __shared_ptr::operator=): Constrain
template with _SaveConf, _Compatible and _Assignable. Remove
__glibcxx_function_requires concept checks. Add static assertion for
deleter expression being well-formed.
(__shared_ptr::__shared_ptr(__shared_ptr<_Tp1>, _Tp*))
(__shared_ptr::operator*, __shared_ptr::operator->)
(__shared_ptr::get, __shared_ptr::_M_ptr): Use element_type instead
of _Tp.
(operator<): Likewise.
(operator>): Define in terms of operator<.
(static_pointer_cast, const_pointer_cast, dynamic_pointer_cast): Use
element_type instead of _Tp.
(reinterpret_pointer_cast): Define for C++17.
(weak_ptr::_Convertible): Replace with _Compatible.
(weak_ptr::_Compatible, weak_ptr::_Assignable): New constraints for
conversions from other types of weak_ptr and shared_ptr.
(__weak_ptr::__weak_ptr, __weak_ptr::operator=): Constrain templates
with _Constructible and _Assignable.
(__weak_ptr::_M_ptr): Use element_type instead of _Tp.
* testsuite/20_util/shared_ptr/assign/auto_ptr_neg.cc: Adjust
dg-error pattern.
* testsuite/20_util/shared_ptr/cons/auto_ptr.cc: Test conversions.
* testsuite/20_util/shared_ptr/cons/unique_ptr.cc: Likewise.
* testsuite/20_util/shared_ptr/cons/void_neg.cc: Likewise.
* testsuite/20_util/shared_ptr/casts/reinterpret.cc: New test.
From-SVN: r241373
* include/backward/auto_ptr.h (__shared_ptr(auto_ptr&&)): Call
_M_enable_shared_from_this_with instead of
__enable_shared_from_this_helper.
* include/bits/shared_ptr.h (__enable_shared_from_this_helper):
Remove overload for std::enable_shared_from_this..
(__enable_shared_from_this_base): Define friend function to select a
std::enable_shared_from_this base class.
* include/bits/shared_ptr_base.h (__enable_shared_from_this_helper):
Remove all overloads.
(__shared_ptr): Change all relevant constructors to call
_M_enable_shared_from_this_with instead of
__enable_shared_from_this_helper.
(__shared_ptr::__efst_base_t, __shared_ptr::__has_efst_base): Helpers
to detect accessible and unambiguous enable_shared_from_this bases.
(__shared_ptr::_M_enable_shared_from_this_with): New function to
replace __enable_shared_from_this_helper overloads.
(__enable_shared_from_this_helper): Remove overload for
std::__enable_shared_from_this.
(__enable_shared_from_this_base): Define friend function to select a
std::__enable_shared_from_this base class.
* include/experimental/bits/shared_ptr.h (experimental::shared_ptr):
Change relevant constructors to call _M_enable_shared_from_this_with.
(experimental::shared_ptr::__efst_base_t)
(experimental::shared_ptr::__has_efst_base): Helpers to detect
accessible and unambiguous enable_shared_from_this bases.
(experimental::shared_ptr::_M_enable_shared_from_this_with): Define.
(experimental::__enable_shared_from_this_helper): Remove overload for
std::experimental::enable_shared_from_this.
(experimental::__expt_enable_shared_from_this_base): Define friend
function to select a std::experimental::enable_shared_from_this base.
* testsuite/experimental/memory/shared_ptr/cons/
enable_shared_from_this.cc: New test.
* testsuite/experimental/memory/shared_ptr/cons/unique_ptr_ctor.cc:
Adjust expected behaviour for shared_ptr<A[]>.
From-SVN: r241353
* include/bits/shared_ptr.h (_Assignable): New alias template.
(shared_ptr::operator=(const shared_ptr<_Tp1>&))
(shared_ptr::operator=(shared_ptr<_Tp1>&&))
(shared_ptr::operator=(unique_ptr<_Tp1>&&)): Constrain with
_Assignable.
* include/bits/shared_ptr_base.h (_Assignable): New alias template.
(__shared_ptr::operator=(const __shared_ptr<_Tp1>&))
(__shared_ptr::operator=(__shared_ptr<_Tp1>&&))
(__shared_ptr::operator=(unique_ptr<_Tp1>&&)): Constrain with
_Assignable.
(__shared_ptr::reset(_Tp1*), __shared_ptr::reset(_Tp1*, _Deleter))
(__shared_ptr::reset(_Tp1*, _Deleter, _Alloc)): Constrain with
_Convertible.
* testsuite/20_util/shared_ptr/cons/43820_neg.cc: Change dg-error to
match on any line.
* testsuite/20_util/shared_ptr/cons/void_neg.cc: Likewise.
* testsuite/20_util/shared_ptr/assign/sfinae.cc: New test.
* testsuite/20_util/shared_ptr/assign/shared_ptr_neg.cc: Update
expected errors. Remove unnecessary code.
* testsuite/20_util/shared_ptr/modifiers/reset_sfinae.cc: New test.
From-SVN: r239898
* testsuite/20_util/enable_shared_from_this/members/reinit.cc: Use
effective target not dg-options. Move check for feature-test macro to:
* testsuite/20_util/enable_shared_from_this/members/weak_from_this.cc:
New test.
From-SVN: r239121
* include/bits/shared_ptr.h (__enable_shared_from_this_helper): Use
nullptr.
* include/bits/shared_ptr_base.h (weak_ptr::_M_assign): Don't assign
if ownership is already shared with a shared_ptr object.
(__enable_shared_from_this_helper): Use nullptr.
* testsuite/20_util/enable_shared_from_this/members/const.cc: New.
* testsuite/20_util/enable_shared_from_this/members/reinit.cc: New.
* testsuite/20_util/enable_shared_from_this/requirements/
explicit_instantiation.cc: Instantiate with const and incomplete types.
From-SVN: r227232
2014-01-28 Jonathan Wakely <jwakely@redhat.com>
Kyle Lippincott <spectral@google.com>
PR libstdc++/59656
* include/bits/shared_ptr.h (shared_ptr): Add new non-throwing
constructor and grant friendship to weak_ptr.
(weak_ptr::lock()): Use new constructor.
* include/bits/shared_ptr_base.h
(_Sp_counted_base::_M_add_ref_lock_nothrow()): Declare new function
and define specializations.
(__shared_count): Add new non-throwing constructor.
(__shared_ptr): Add new non-throwing constructor and grant friendship
to __weak_ptr.
(__weak_ptr::lock()): Use new constructor.
* testsuite/20_util/shared_ptr/cons/43820_neg.cc: Adjust dg-error.
* testsuite/20_util/shared_ptr/cons/void_neg.cc: Likewise.
Co-Authored-By: Kyle Lippincott <spectral@google.com>
From-SVN: r207180
PR c++/50500
DR 1082
* class.c (type_has_user_declared_move_constructor): New.
(type_has_user_declared_move_assign): New.
(add_implicitly_declared_members): Add lazy copy ops
even if there's a move.
* method.c (lazily_declare_fn): Delete implicit copies
if there's a move.
(maybe_explain_implicit_delete): Explain this. Use inform rather
than error.
* cp-tree.h: Declare new fns.
From-SVN: r180159
2011-05-18 Jonathan Wakely <jwakely.gcc@gmail.com>
* include/bits/shared_ptr_base.h: Use noexcept. Define special member
functions as defaulted/deleted.
* include/bits/shared_ptr.h: Use noexcept.
* 20_util/shared_ptr/cons/43820_neg.cc: Adjust dg-error line numbers.
* 20_util/weak_ptr/comparison/cmp_neg.cc: Likewise.
From-SVN: r173882
2011-03-22 Paolo Carlini <paolo.carlini@oracle.com>
* include/bits/shared_ptr.h (operator>, operator<=, operator>=): Add,
per DR 1401.
(operator==, operator!=, operator<): Fix per the letter of DR 1401.
* include/bits/shared_ptr_base.h: Likewise for __shared_ptr.
* include/bits/unique_ptr.h (operator==, operator!=, operator<,
operator<=, operator>, operator>=): Fix per the letter of DR 1401.
* testsuite/20_util/shared_ptr/comparison/dr1401.cc: New.
* testsuite/20_util/unique_ptr/comparison/dr1401.cc: Likewise.
* testsuite/20_util/weak_ptr/comparison/cmp_neg.cc: Adjust.
From-SVN: r171293
