Summary:
The `[[nodiscard]]` attribute is intended to help users find bugs where
function return values are ignored when they shouldn't be. After C++17 the
C++ standard has started to declared such library functions as `[[nodiscard]]`.
However, this application is limited and applies only to dialects after C++17.
Users who want help diagnosing misuses of STL functions may desire a more
liberal application of `[[nodiscard]]`.
For this reason libc++ provides an extension that does just that! The
extension must be enabled by defining `_LIBCPP_ENABLE_NODISCARD`. The extended
applications of `[[nodiscard]]` takes two forms:
1. Backporting `[[nodiscard]]` to entities declared as such by the
standard in newer dialects, but not in the present one.
2. Extended applications of `[[nodiscard]]`, at the libraries discretion,
applied to entities never declared as such by the standard.
Users may also opt-out of additional applications `[[nodiscard]]` using
additional macros.
Applications of the first form, which backport `[[nodiscard]]` from a newer
dialect may be disabled using macros specific to the dialect it was added. For
example `_LIBCPP_DISABLE_NODISCARD_AFTER_CXX17`.
Applications of the second form, which are pure extensions, may be disabled
by defining `_LIBCPP_DISABLE_NODISCARD_EXT`.
This patch was originally written by me (Roman Lebedev),
then but then reworked by Eric Fiselier.
Reviewers: mclow.lists, thakis, EricWF
Reviewed By: thakis, EricWF
Subscribers: llvm-commits, mclow.lists, lebedev.ri, EricWF, rjmccall, Quuxplusone, cfe-commits, christof
Differential Revision: https://reviews.llvm.org/D45179
llvm-svn: 342808
This constructor needs to cast a pointer to uninitialized
memory to a pointer to object type in order to call
allocator_traits::construct(). This cast is not allowed when CFI cast
checks are enabled.
I did this instead of marking __addr() as _LIBCPP_NO_CFI so that we
don't lose CFI checks on get() or the dtor.
Differential Revision: https://reviews.llvm.org/D50743
llvm-svn: 339797
Summary:
We never actually mean to always inline a function -- all the uses of
the macro I could find are actually attempts to control the visibility
of symbols. This is better described by _LIBCPP_INLINE_VISIBILITY, which
is actually always defined the same.
This change is orthogonal to the decision of what we're actually going
to do with _LIBCPP_INLINE_VISIBILITY -- it just simplifies things by
having one canonical way of doing things.
Note that this commit had originally been applied in r336369 and then
reverted in r336382 because of unforeseen problems. Both of these problems
have now been fixed.
Reviewers: EricWF, mclow.lists
Subscribers: christof, dexonsmith, erikvanderpoel
Differential Revision: https://reviews.llvm.org/D48892
llvm-svn: 336866
This reverts commit r336369. The commit had two problems:
1. __pbump was marked as _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY instead of
_LIBCPP_INLINE_VISIBILITY, which lead to two symbols being added in the
dylib and the check-cxx-abilist failing.
2. The LLDB tests started failing because they undefine
`_LIBCPP_INLINE_VISIBILITY`. I need to figure out why they do that and
fix the tests before we can go forward with this change.
llvm-svn: 336382
Summary:
We never actually mean to always inline a function -- all the uses of
the macro I could find are actually attempts to control the visibility
of symbols. This is better described by _LIBCPP_INLINE_VISIBILITY, which
is actually always defined the same.
This change is orthogonal to the decision of what we're actually going
to do with _LIBCPP_INLINE_VISIBILITY -- it just simplifies things by
having one canonical way of doing things.
Reviewers: EricWF
Subscribers: christof, llvm-commits, dexonsmith, erikvanderpoel, mclow.lists
Differential Revision: https://reviews.llvm.org/D48892
llvm-svn: 336369
This patch fixes std::allocator, and more specifically, all users
of __libcpp_allocate and __libcpp_deallocate, to support over-aligned
types.
__libcpp_allocate/deallocate now take an alignment parameter, and when
the specified alignment is greater than that supported by malloc/new,
the aligned version of operator new is called (assuming it's available).
When aligned new isn't available, the old behavior has been kept, and the
alignment parameter is ignored.
This patch depends on recent changes to __builtin_operator_new/delete which
allow them to be used to call any regular new/delete operator. By using
__builtin_operator_new/delete when possible, the new/delete erasure optimization
is maintained.
llvm-svn: 328180
The specification of this function mandates a cast to uninitialized
T*, which is forbidden under CFI.
Differential Revision: https://reviews.llvm.org/D42146
llvm-svn: 322744
The commit r300140 changed the implementation of compressed_pair, but didn't add
_LIBCPP_INLINE_VISIBILITY to the constructors and get members of the
compressed_pair_elem class. This patch adds the visibility annotation.
I didn't find a way to test this change with libc++ regression tests.
rdar://35352579
Differential Revision: https://reviews.llvm.org/D39751
llvm-svn: 317816
There were a number of cases where __double_underscore functions,
for example __has_construct_test, were called without being qualified,
causing ADL to occur. This patch qualifies those calls to avoid this
problem.
Thanks to David L. Jones for point out the issue initially.
llvm-svn: 313324
Summary:
This patch improves how libc++ handles min/max macros within the headers. Previously libc++ would undef them and emit a warning.
This patch changes libc++ to use `#pragma push_macro` to save the macro before undefining it, and `#pragma pop_macro` to restore the macros and the end of the header.
Reviewers: mclow.lists, bcraig, compnerd, EricWF
Reviewed By: EricWF
Subscribers: cfe-commits, krytarowski
Differential Revision: https://reviews.llvm.org/D33080
llvm-svn: 304357
Summary:
This patch fixes bugs.llvm.org/PR32979.
[util.smartptr.shared.const] says:
> In the constructor definitions below, enables shared_from_this with p, for a pointer p of type Y*, means
> that if Y has an unambiguous and accessible base class that is a specialization of enable_shared_from_-
> this.
This means that libc++ needs to respect the access specifier of the base class, and not attempt to construct
and enabled_shared_from_this base if it is private. However access specifiers don't affect overload resolution
so our current implementation will attempt to construct the private base.
This patch uses SFINAE to correctly detect if the shared_ptr input has an accessible enable_shared_from_this
base class.
Reviewers: mclow.lists
Reviewed By: mclow.lists
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D33033
llvm-svn: 302709
Libc++ is used as a system library on macOS and iOS (amongst others). In order
for users to be able to compile a binary that is intended to be deployed to an
older version of the platform, clang provides the
availability attribute <https://clang.llvm.org/docs/AttributeReference.html#availability>_
that can be placed on declarations to describe the lifecycle of a symbol in the
library.
See docs/DesignDocs/AvailabilityMarkup.rst for more information.
Differential Revision: https://reviews.llvm.org/D31739
llvm-svn: 302172
This patch overhauls both specializations of unique_ptr while implementing
the following LWG issues:
* LWG 2801 - This issue constrains unique_ptr's constructors when the deleter type
is not default constructible. Additionally it adds SFINAE conditions
to unique_ptr<T[]>::unique_ptr(Up).
* LWG 2905 - This issue reworks the unique_ptr(pointer, /* see below */ deleter)
constructors so that they correctly SFINAE when the deleter argument cannot
be used to construct the stored deleter.
* LWG 2520 - This issue fixes initializing unique_ptr<T[]> from nullptr.
Libc++ had previously implemented this issue, but the suggested resolution
still broke initialization from NULL. This patch re-works the
unique_ptr<T[]>(Up, deleter) overloads so that they accept NULL as well
as nullptr.
llvm-svn: 300406
Summary:
__compressed_pair takes and passes it's constructor arguments by value. This causes arguments to be moved 3 times instead of once. This patch addresses that issue and fixes `constexpr` on the constructors.
I would rather have this fix than D27564, and I'm fairly confident it's not ABI breaking but I'm not 100% sure.
I prefer this solution because it removes a lot of code and makes the implementation *much* smaller.
Reviewers: mclow.lists, K-ballo
Reviewed By: K-ballo
Subscribers: K-ballo, cfe-commits
Differential Revision: https://reviews.llvm.org/D27565
llvm-svn: 300140
For reference deleter types the const qualifier on the return type
of get_deleter() should be ignored, and a non-const deleter should
be returned.
This patch fixes a bug where "const deleter_type&" is incorrectly
formed.
llvm-svn: 300121
Summary:
Exactly what the title says.
This patch also adds a `std::hash<nullptr_t>` specialization in C++17, but it was not added by this paper and I can't find the actual paper that adds it.
See http://wg21.link/P0513R0 for more info.
If there are no comments in the next couple of days I'll commit this
Reviewers: mclow.lists, K-ballo, EricWF
Reviewed By: EricWF
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D28938
llvm-svn: 292684
In order to allow inlining of previously out-of-line functions without an ABI break
libc++ provides legacy definitions in the dylib that old programs can
continue to use. Unfortunatly Windows link.exe detects this hack and diagnoses the duplicate
definitions.
This patch disable the duplicate definitions on Windows by adding an ABI option
which disables all "legacy out-of-line symbols"
llvm-svn: 292190
Moves hot functions such as atomic add into the memory header file
so that they can be inlined, which brings performance benefits.
Patch by Kevin Hu, Aditya Kumar, Sebastian Pop
Differential Revision: https://reviews.llvm.org/D24991
llvm-svn: 292184
Summary:
Some parts of the FreeBSD tree are still compiled with C++98, and until
rL288554 this has always worked fine. After that, a complaint about the
newly introduced local _PairT is produced:
/usr/include/c++/v1/memory:3354:27: error: template argument uses local type '_PairT' [-Werror,-Wlocal-type-template-args]
typedef __scalar_hash<_PairT> _HashT;
^~~~~~
/usr/include/c++/v1/memory:3284:29: error: template argument uses local type '_PairT' [-Werror,-Wlocal-type-template-args]
: public unary_function<_Tp, size_t>
^~~
/usr/include/c++/v1/memory:3356:12: note: in instantiation of template class 'std::__1::__scalar_hash<_PairT, 2>' requested here
return _HashT()(__p);
^
As far as I can see, there should be no problem moving the _PairT
struct to just before the __hash_combine() function, which fixes this
particular warning.
Reviewers: mclow.lists, EricWF
Subscribers: cfe-commits, emaste
Differential Revision: https://reviews.llvm.org/D28472
llvm-svn: 291476
Summary:
On Windows the identifier `__deallocate` is defined as a macro by one of the Windows system headers. Previously libc++ worked around this by `#undef __deallocate` and generating a warning. However this causes the WIN32 version of `__threading_support` to always generate a warning on Windows. This is not OK.
This patch renames all usages of `__deallocate` internally as to not conflict with the macro.
Reviewers: mclow.lists, majnemer, rnk, rsmith, smeenai, compnerd
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D28426
llvm-svn: 291332
In ABI v1 libc++ implements std::pointer_safety as a class type instead
of an enumeration. However this class type does not provide
a default constructor as it should. This patch adds that default constructor.
llvm-svn: 291059
In the C++ standard `std::pointer_safety` is defined
as a C++11 strongly typed enum. However libc++ currently defines
it as a class type which simulates a C++11 enumeration. This
can be detected in valid C++ code.
This patch introduces an the _LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE ABI option.
When defined `std::pointer_safety` is implemented as an enum type.
Unfortunatly this also means it can no longer be provided as an extension
in C++03.
Additionally this patch moves the definition for `get_pointer_safety()`
out of the dylib, and into the headers. New usages of `get_pointer_safety()`
will now use the inline version instead of the dylib version. However in
order to keep the dylib ABI compatible the old definition is explicitly
compiled into it.
llvm-svn: 291046
The name _LIBCPP_TYPE_VIS_ONLY is no longer accurate because both
_LIBCPP_TYPE_VIS and _LIBCPP_TYPE_VIS_ONLY expand to
__attribute__((__type_visibility__)) with Clang. The only remaining difference
is that _LIBCPP_TYPE_VIS_ONLY can be applied to templates whereas
_LIBCPP_TYPE_VIS cannot (due to dllimport/dllexport not being allowed on
templates).
This patch renames _LIBCPP_TYPE_VIS_ONLY to _LIBCPP_TEMPLATE_VIS.
llvm-svn: 291035
libc++ no longer supports C++11 compilers that don't implement `= default`.
This patch removes all instances of the feature test macro
_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS as well as the potentially dead code it hides.
llvm-svn: 287321
Summary:
Libc++ still uses per-feature configuration macros when configuring for C++11. However libc++ requires a feature-complete C++11 compiler so there is no reason to check individual features. This patch starts the process of removing the feature specific macros and replacing their usage with `_LIBCPP_CXX03_LANG`.
This patch removes the __config macros:
* _LIBCPP_HAS_NO_TRAILING_RETURN
* _LIBCPP_HAS_NO_TEMPLATE_ALIASES
* _LIBCPP_HAS_NO_ADVANCED_SFINAE
* _LIBCPP_HAS_NO_DEFAULT_FUNCTION_TEMPLATE_ARGS
* _LIBCPP_HAS_NO_STATIC_ASSERT
As a drive I also changed our C++03 static_assert to use _Static_assert if available.
I plan to commit this without review if nobody voices an objection.
Reviewers: mclow.lists
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D24895
llvm-svn: 282347
call_once is using relaxed atomic load to perform double-checked locking, which contains a data race. The fast-path load has to be an acquire atomic load.
Differential Revision: https://reviews.llvm.org/D24028
llvm-svn: 280621
This patch adds the weak_type typedef in shared_ptr. It is available in
C++17 and newer.
This patch also updates the _LIBCPP_STD_VER and TEST_STD_VER macros to
have the value of 16, since 2016 is the current year.
llvm-svn: 273839
See https://llvm.org/bugs/show_bug.cgi?id=27115
The problem was that the conversion from
'const enable_shared_from_this<T>*' to 'const T*' didn't work if
T inherited enable_shared_from_this as a virtual base class. The fix
is to take the original pointer passed to shared_ptr's constructor in the
__enable_weak_this method and perform an upcast to 'const T*' instead of
performing a downcast from the enable_shared_from_this base.
llvm-svn: 273835
Summary:
Currently the implementation of [util.smartptr.shared.atomic] is provided only when using Clang, and not with GCC. This is a relic of not having a GCC implementation of <atomic>, even though <atomic> isn't actually used in the implementation. This patch enables support for atomic shared_ptr functions when using GCC.
Note that this is not a header only change. Previously only Clang builds of libc++.so would provide the required symbols. There is no reason for this restriction.
After this change both Clang and GCC builds should be binary compatible with each other WRT these symbols.
Reviewers: mclow.lists, rmaprath, EricWF
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D21407
llvm-svn: 273076
When you assign a shared_ptr, the deleter gets called and assigned. In this routine, the assignment happens inside a critical section, which could (potentially) lead to a deadlock, if the deleter did something wonky. Now we swap the old value with an (empty) temporary shared_ptr, and then let the temporary delete the old value when it goes out of scope (after the lock has been released). This should fix PR#27724. Thanks to Hans Boehm for the bug report and the suggested fix.
llvm-svn: 269965
These are the cases when an out-of-class definition of a method is
marked _LIBCPP_INLINE_VISIBILITY, but the in-class declaration is
not. This will start failing when (or if) we switch to
attribute((internal_linkage)).
llvm-svn: 255166
This change moves visibility attributes from out-of-class method
definitions to in-class declaration. This is needed for a switch to
attribute((internal_linkage)) (see http://reviews.llvm.org/D13925)
which can only appear on the first declaration.
This change does not touch istream/ostream/streambuf. They are
handled separately in http://reviews.llvm.org/D14409.
llvm-svn: 252385
Summary:
This patch properly constrains the converting assignment operator in C++03. It also fixes a bug where std::forward was given the wrong type.
The following two tests begin passing in C++03:
* `unique_ptr.single.asgn/move_convert.pass.cpp`
* `unique_ptr.single.asgn/move_convert13.fail.cpp`
Reviewers: mclow.lists
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D12173
llvm-svn: 246272
Currently we need an #ifdef branch every time we use pointer traits to rebind a pointer because
it is done differently in C++11 and C++03. This patch introduces the __rebind_pointer utility to
clean this up.
Also add a test that list and it's iterators can be instantiated with incomplete element types.
llvm-svn: 245806
Currently we need an #ifdef branch every time we use pointer traits to rebind a pointer because
it is done differently in C++11 and C++03. This patch introduces the __rebind_pointer utility to
clean this up.
llvm-svn: 245802
Summary:
After putting this question up on cfe-dev I have decided that it would be best to allow the use of `<atomic>` in C++03. Although static initialization is a concern the syntax required to get it is C++11 only. Meaning that C++11 constant static initialization cannot silently break in C++03, it will always cause a syntax error. Furthermore `ATOMIC_VAR_INIT` and `ATOMIC_FLAG_INIT` remain defined in C++03 even though they cannot be used because C++03 usages will cause better error messages.
The main change in this patch is to replace `__has_feature(cxx_atomic)`, which only returns true when C++ >= 11, to `__has_extension(c_atomic)` which returns true whenever clang supports the required atomic builtins.
This patch adds the following macros:
* `_LIBCPP_HAS_C_ATOMIC_IMP` - Defined on clang versions which provide the C `_Atomic` keyword.
* `_LIBCPP_HAS_GCC_ATOMIC_IMP` - Defined on GCC > 4.7. We must use the fallback atomic implementation.
* `_LIBCPP_HAS_NO_ATOMIC_HEADER` - Defined when it is not safe to include `<atomic>`.
`_LIBCPP_HAS_C_ATOMIC_IMP` and `_LIBCPP_HAS_GCC_ATOMIC_IMP` are mutually exclusive, only one should be defined. If neither is defined then `<atomic>` is not implemented and including `<atomic>` will issue an error.
Reviewers: chandlerc, jroelofs, mclow.lists
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D11555
llvm-svn: 245463
Although CMake adds warning flags, they are ignored in the libc++ headers
because the headers '#pragma system header' themselves.
This patch disables the system header pragma when building libc++ and fixes
the warnings that arose.
The warnings fixed were:
1. <memory> - anonymous structs are a GNU extension
2. <functional> - anonymous structs are a GNU extension.
3. <__hash_table> - Embedded preprocessor directives have undefined behavior.
4. <string> - Definition is missing noexcept from declaration.
5. <__std_stream> - Unused variable.
llvm-svn: 242623
Summary:
In some places in libc++ we need to use the `__atomic_*` builtins. This patch adds a header that provides access to those builtins in a uniform way from within the dylib source.
If the compiler building the dylib does not support these builtins then a warning is issued.
Only relaxed loads are needed within the headers. A singe function to do these relaxed loads has been added to `<memory>`.
This patch applies the new atomic builtins to `__shared_count` and `call_once`.
Reviewers: mclow.lists
Subscribers: majnemer, jroelofs, cfe-commits
Differential Revision: http://reviews.llvm.org/D10406
llvm-svn: 241532
Roman Lebedev