On targets that have limited atomic support, e.g. ones that define
ATOMIC_*_LOCK_FREE to '1' ("sometimes lock free"), we would end up
referencing yet-undefined __libcpp_{,un}signed_lock_free.
This commit adds a guard to prevent these references for such
targets.
Differential Revision: https://reviews.llvm.org/D118391
This change is the basis for a further refactoring where I'm going to
split up the various implementations we have in __threading_support to
make that code easier to understand.
Note that I had to make __convert_to_timespec a template to break
circular dependencies. Concretely, we never seem to use it with anything
other than ::timespec, but I am wary of hardcoding that assumption as
part of this change, since I suspect there's a reason for going through
these hoops in the first place.
Differential Revision: https://reviews.llvm.org/D116944
When P0883R2 was initially implemented in D103769 #pragma clang deprecated didn't exist yet.
We also forgot to cleanup usages in libc++ itself.
This takes care of both.
Differential Revision: https://reviews.llvm.org/D115995
clang has `= default` as an extension in c++03, so just use it.
Reviewed By: ldionne, Quuxplusone, #libc
Spies: libcxx-commits
Differential Revision: https://reviews.llvm.org/D115275
std::atomic is, for the most part, just a thin veneer on top of compiler
builtins. Hence, it should be available even when threads are not available
on the system, and in fact there has been requests for such support.
This patch:
- Moves __libcpp_thread_poll_with_backoff to its own header so it can
be used in <atomic> when threads are disabled.
- Adds a dummy backoff policy for atomic polling that doesn't know about
threads.
- Adjusts the <atomic> feature-test macros so they are provided even when
threads are disabled.
- Runs the <atomic> tests when threads are disabled.
rdar://77873569
Differential Revision: https://reviews.llvm.org/D114109
We've stopped doing it in libc++ for a while now because these names
would end up rotting as we move things around and copy/paste stuff.
This cleans up all the existing files so as to stop the spreading
as people copy-paste headers around.
- Replace irrelevant synopsis by a comment
- Use a .verify.cpp test instead of .compile.fail.cpp
- Remove unnecessary includes in one of the tests (was a copy-paste error)
Differential Revision: https://reviews.llvm.org/D114094
While looking at LWG-2988 and P0558 it seems the issues were already
implemented, but the synopsis wasn't updated. Some of the tests didn't
validate the `noexcept` status. A few tests were missing completely:
- `atomic_wait_explicit`
- `atomic_notify_one`
- `atomic_notify_all`
Mark P0558 as complete, didn't investigate which version of libc++ first
includes this. It seems the paper has been retroactively applied. I
couldn't find whether this is correct, but looking at cppreference it
seems intended.
Completes
- LWG-2988 Clause 32 cleanup missed one typename
- P0558 Resolving atomic<T> named base class inconsistencies
Reviewed By: #libc, ldionne
Differential Revision: https://reviews.llvm.org/D103765
Some embedded platforms do not wish to support the C library functionality
for handling wchar_t because they have no use for it. It makes sense for
libc++ to work properly on those platforms, so this commit adds a carve-out
of functionality for wchar_t.
Unfortunately, unlike some other carve-outs (e.g. random device), this
patch touches several parts of the library. However, despite the wide
impact of this patch, I still think it is important to support this
configuration since it makes it much simpler to port libc++ to some
embedded platforms.
Differential Revision: https://reviews.llvm.org/D111265
While looking at the review comments in D103765 there was an oddity in
the tests for the following functions:
- atomic_fetch_add
- atomic_fetch_add_explicit
- atomic_fetch_sub
- atomic_fetch_sub_explicit
Libc++ allows usage of
`atomic_fetch_add<int>(atomic<int*>*, atomic<int*>::difference_type);`
MSVC and GCC reject this code: https://godbolt.org/z/9d8WzohbE
This makes the atomic `fetch(add|sub).*` Standard conforming and removes the non-conforming extensions.
Fixes PR47908
Reviewed By: ldionne, #libc
Differential Revision: https://reviews.llvm.org/D103983
There is a lot more we can do, in particular in <type_traits>, but this
removes some workarounds that were gated on checking a specific compiler
version.
Differential Revision: https://reviews.llvm.org/D108923
https://eel.is/c++draft/atomics.types.operations#23 says: ... the value of failure is order except that a value of `memory_order::acq_rel` shall be replaced by the value `memory_order::acquire` and a value of `memory_order::release` shall be replaced by the value `memory_order::relaxed`.
This failure mapping is only handled for `_LIBCPP_HAS_GCC_ATOMIC_IMP`. We are seeing bad code generation for `compare_exchange_strong(cmp, 1, std::memory_order_acq_rel)` when using libc++ in place of libstdc++: https://godbolt.org/z/v3onrrq4G.
This was caught by tsan tests after D99434, `[TSAN] Honor failure memory orders in AtomicCAS`, but appears to be an issue in non-tsan code.
Reviewed By: ldionne, dvyukov
Differential Revision: https://reviews.llvm.org/D103846
Add deleted volatile copy-assignment operator in the most derived atomic
to fix the Bug 41784. The root cause: there is an `operator=(T) volatile`
that has better match than the deleted copy-assignment operator of the base
class when `this` is `volatile`. The compiler sees that right operand of
the assignment operator can be converted to `T` and chooses that path
without taking into account the deleted copy-assignment operator of the
base class.
The current behavior on libstdc++ is different from what we have in libc++.
On the same test compilation fails with libstdc++. Proof: https://godbolt.org/z/nebPYd
(everything is the same except the -stdlib option).
I choose the way with explicit definition of copy-assignment for atomic
in the most derived class. But probably we can fix that by moving
`operator=(T)` overloads to the base class from both specializations.
At first glance, it shouldn't break anything.
Differential Revision: https://reviews.llvm.org/D90968
Generally these calls aren't vulnerable to ADL because they involve only
primitive types. The ones in <list> and <vector> drag in namespace std
but that's OK; the ones in <fstream> and <strstream> are vulnerable
iff `CharT` is an enum type, which seems far-fetched.
But absolutely zero of them *need* ADL to happen; so in my opinion
they should all be consistently qualified, just like calls to any
other (non-user-customizable) functions in namespace std.
Also: Include <cstring> and <cwchar> in <__string>.
We seemed to be getting lucky that <memory> included <iterator>
included <iosfwd> included <wchar.h>. That gave us the
global-namespace `wmemmove`, but not `_VSTD::wmemmove`.
This is now fixed.
I didn't touch these headers:
<ext/__hash> uses strlen, safely
<support/ibm/locale_mgmt_aix.h> uses memcpy, safely
<string.h> uses memchr and strchr, safely
<wchar.h> uses wcschr, safely
<__bsd_locale_fallbacks.h> uses wcsnrtombs, safely
Differential Revision: https://reviews.llvm.org/D93061
Currently, vendor-specific availability markup is enabled by default.
This means that even when building against trunk libc++, the headers
will by default prevent you from using some features that were not
released in the dylib on your target platform. This is a source of
frustration since people building libc++ from sources are usually not
trying to use some vendor's released dylib.
For that reason, I've been thinking for a long time that availability
annotations should be off by default, which is the primary change that
this commit enables.
In addition, it reworks the implementation to make it easier for new
vendors to add availability annotations for their platform, and it
refreshes the documentation to reflect the current state of the codebase.
Finally, a CMake configuration option is added to control whether
availability annotations should be turned on for the flavor of libc++
being created. The intent is for vendors like Apple to turn it on, and
for the upstream libc++ to leave it off (the default).
Differential Revision: https://reviews.llvm.org/D90843
- Avoid using C++11-and-later features in <atomic>:
Historically, we've supported <atomic> in C++03, so we can't use C++11
features in that header. This is something we really need to change,
since our implementation of <atomic> is starting to accumulate technical
debt because of that.
- Mark a test as unsupported on single threaded systems
- Add missing symbols to the Linux ABI list
- Add the new symbols to the ABI list on Darwin
- Add XFAIL markup to the tests that require dylib support on older platforms
- Add availability markup for back-deployment
An upcoming change in Clang will flag _Atomic as being a C11 extension.
To avoid generating this warning in libc++, this commit marks the only
use of _Atomic with the __extension__ extension, which suppresses such
warnings.
llvm-svn: 370796
The CMake CheckLibcxxAtomic module was always failing to compile
the example, even when libatomic wasn't needed. This was caused
because the check doesn't link a C++ runtime library to provide
std::terminate, which is required for exception support.
The check is still really broken, but <atomic> is better!
llvm-svn: 364146
Summary:
We need to pin the underlying type of C++20' `std::memory_order` to match the C++17 version. Anything less is an ABI break.
At the moment it's `unsigned` before C++20 and `int` after. Or if you're using `-fshort-enums` it's `unsigned char` before C++20 and `int` after.
This patch explicitly specifies the underlying type of the C++20 `memory_order` to be w/e type the compiler would have chosen for the C++17 version.
Reviewers: mclow.lists, ldionne
Reviewed By: ldionne
Subscribers: jfb, jdoerfert, #libc, zoecarver
Differential Revision: https://reviews.llvm.org/D59063
llvm-svn: 355755
Summary:
This breaks ABI for folks using -fshort-enums, and does not really buy
us anything.
http://llvm.org/PR40977
Reviewers: mclow.lists, EricWF
Subscribers: christof, jkorous, dexonsmith, libcxx-commits, zoecarver
Differential Revision: https://reviews.llvm.org/D59029
llvm-svn: 355521
Revert "[libc++] Fix <atomic> failures on GCC"
Revert "[libc++] Change memory_order to an enum class"
Revert "[libc++] decoupling Freestanding atomic<T> from libatomic.a"
The lldb formatter nededs to be updated. Shafik and Louis will
coordinate to do so.
llvm-svn: 355417
Summary:
In https://reviews.llvm.org/D58201, we turned memory_order into an enum
class in C++20 mode. However, we were not casting memory_order to its
underlying type correctly for the GCC implementation, which broke the
build bots. I also fixed a test that was failing in C++17 mode on GCC 5.
Reviewers: EricWF, jfb, mclow.lists
Subscribers: zoecarver
Differential Revision: https://reviews.llvm.org/D58966
llvm-svn: 355409
This patch introduces non-lockfree atomics that do not require using
an external libatomic. This work is done with the long-term goal of
allowing the use of <atomic> in freestanding environments.
Thanks to Olivier Giroux for the patch.
Differential Revision: https://reviews.llvm.org/D56913
llvm-svn: 355318
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
Summary:
C++11 onwards specs the non-member functions atomic_load and atomic_load_explicit as taking the atomic<T> by const (potentially volatile) pointer. C11, in its infinite wisdom, decided to drop the const, and C17 will fix this with DR459 (the current draft forgot to fix B.16, but that’s not the normative part).
This patch fixes the libc++ version of the __c11_atomic_load builtins defined for GCC's compatibility sake.
D47618 takes care of the clang side.
Discussion: http://lists.llvm.org/pipermail/cfe-dev/2018-May/058129.html
<rdar://problem/27426936>
Reviewers: EricWF, mclow.lists
Subscribers: christof, cfe-commits
Differential Revision: https://reviews.llvm.org/D47613
llvm-svn: 333776
That's r333325, as well as follow-up "Fix GCC handling of ATOMIC_VAR_INIT"
r333327.
Marshall asked to revert:
Let's have a discussion about how to implement this so that it is more friendly
to people with installed code bases. We've had *extremely* loud responses to
unilaterally adding warnings - especially ones that can't be easily disabled -
to the libc++ code base in the past.
llvm-svn: 333351
Summary:
The atomic non-member functions accept pointers to std::atomic / std::atomic_flag as well as to the non-atomic value. These are all dereferenced unconditionally when lowered, and therefore will fault if null. It's a tiny gotcha for new users, especially when they pass in NULL as expected value (instead of passing a pointer to a NULL value). We can therefore use the nonnull attribute to denote that:
- A warning should be generated if the argument is null
- It is undefined behavior if the argument is null (because a dereference will segfault)
This patch adds support for this attribute for clang and GCC, and sticks to the subset of the syntax both supports. In particular, work around this GCC oddity:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60625
The attributes are documented:
- https://gcc.gnu.org/onlinedocs/gcc-4.0.0/gcc/Function-Attributes.html
- https://clang.llvm.org/docs/AttributeReference.html#nullability-attributes
I'm authoring a companion clang patch for the __c11_* and __atomic_* builtins, which currently only warn on a subset of the pointer parameters.
In all cases the check needs to be explicit and not use the empty nonnull list, because some of the overloads are for atomic<T*> and the values themselves are allowed to be null.
<rdar://problem/18473124>
Reviewers: arphaman, EricWF
Subscribers: aheejin, christof, cfe-commits
Differential Revision: https://reviews.llvm.org/D47225
llvm-svn: 333325
C11 defines `kill_dependency` as a macro in <stdatomic.h>. When you
include <atomic> after <stdatomic.h>, the macro clashes with
`std::kill_dependency` and causes multiple errors. Explicit error should
help in diagnosing those errors.
No change for working code that includes <atomic> before <stdatomic.h>.
rdar://problem/27435938
Reviewers: rsmith, EricWF, mclow.lists, jfb
Reviewed By: jfb
Subscribers: jfb, jkorous-apple, christof, bumblebritches57, JonChesterfield, smeenai, cfe-commits
Differential Revision: https://reviews.llvm.org/D45470
llvm-svn: 332413
Arthur O'Dwyer