I recently came across LIBCXXABI_USE_LLVM_UNWINDER and was surprised to
notice it was disabled by default. Since we build libunwind by default
and ship it in the LLVM toolchain, it would seem to make sense that
libc++ and libc++abi rely on libunwind for unwinding instead of using
the system-provided unwinding library (if any).
Most importantly, using the system unwinder implies that libc++abi is
ABI compatible with that system unwinder, which is not necessarily the
case. Hence, it makes a lot more sense to instead default to using the
known-to-be-compatible LLVM unwinder, and let vendors manually select a
different unwinder if desired.
As a follow-up change, we should probably apply the same default to
compiler-rt.
Differential Revision: https://reviews.llvm.org/D150897Fixes#77662
rdar://120801778
As pointed out by @Zingam the paper was implemented in libc++ as an
extension. This patch does the bookkeeping. The inital release version
is based on historical release dates.
Completes:
- Add a conditional noexcept specification to std::apply
fixes#70506
The detailed problem description is in #70506
The original proposed fix was to remove `[[no_unique_address]]` except
when `_Tp` is empty.
Edit:
After the discussion in the comments below, the new fix here is to
remove the `[[no_unique_address]]` from `movable_box` in the cases where
we need to add our own assignment operator, which has contains the
problematic `construct_at`
The status table incorrectly marks P0521R0 as nothing to do. This is not
correct the function should be deprecated.
During our latest monthly meeting we argreed to remove the
_LIBCPP_ENABLE_CXXyy_REMOVED_FEATURES macros, therefore the new macro is
not
added to that global list.
Implements
- P0521R0 Proposed Resolution for CA 14 (shared_ptr use_count/unique)
Implements parts of
- P0619R4 Reviewing Deprecated Facilities of C++17 for C++20
---------
Co-authored-by: Nikolas Klauser <nikolasklauser@berlin.de>
Finishes implementation of
- P2093R14 Formatted output
- P2539R4 Should the output of std::print to a terminal be synchronized
with the underlying stream?
Differential Revision: https://reviews.llvm.org/D156609
This change requires quite a number of changes in the tests; this is not
code I expect people to use in the wild. So I don't expect breakage for
users.
Implements:
- P2905R2 Runtime format strings, as a Defect Report
This paper was voted in as a DR, so it's retroactively enabled back to
C++20; the C++ version that introduced std::format.
Implements:
- P2909R4 Fix formatting of code units as integers (Dude, where’s my
``char``?)
Several experimental headers around std::pmr have been slated for
removal for a while now. This patch actually performs the removal and
cleanups from the code base.
This patch re-introduces special support for narrowing conversions to
bool
in std::variant, which was removed in 170810fca6ee in order to make
libc++
Standards-conforming.
The special support is gated by the
`_LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT`
macro and will be supported for LLVM 18 only as a courtesy to help large
code bases migrate over to the Standard behavior.
---------
Co-authored-by: Bogdan Graur <bgraur@google.com>
Co-authored-by: Louis Dionne <ldionne.2@gmail.com>
This patch brings std::ios_base::noreplace from P2467R1 to libc++.
This requires compiling the shared library in C++23 mode since otherwise
fstream::open(...) doesn't know about the new flag.
Differential Revision: https://reviews.llvm.org/D137640
Co-authored-by: Louis Dionne <ldionne.2@gmail.com>
1. Instead of using individual "boolean" macros, have an "enum" macro
`_LIBCPP_HARDENING_MODE`. This avoids issues with macros being
mutually exclusive and makes overriding the hardening mode within a TU
more straightforward.
2. Rename the safe mode to debug-lite.
This brings the code in line with the RFC:
https://discourse.llvm.org/t/rfc-hardening-in-libc/73925Fixes#65101
This patch implements `std::basic_syncbuf` and `std::basic_osyncstream` as specified in paper p0053r7. ~~For ease of reviewing I am submitting this patch before submitting a patch for `std::basic_osyncstream`. ~~
~~Please note, this patch is not 100% complete. I plan on adding more tests (see comments), specifically I plan on adding tests for multithreading and synchronization.~~
Edit: I decided that it would be far easier for me to keep track of this and make changes that affect both `std::basic_syncbuf` and `std::basic_osyncstream` if both were in one patch.
The patch was originally written by @zoecarver
Implements
- P0053R7 - C++ Synchronized Buffered Ostream
- LWG-3127 basic_osyncstream::rdbuf needs a const_cast
- LWG-3334 basic_osyncstream move assignment and destruction calls basic_syncbuf::emit() twice
- LWG-3570 basic_osyncstream::emit should be an unformatted output function
- LWG-3867 Should std::basic_osyncstream's move assignment operator be noexcept?
Reviewed By: ldionne, #libc
Differential Revision: https://reviews.llvm.org/D67086
According to https://developer.apple.com/support/xcode/, quite a few of
our availability macros don't do anything anymore, so we might as well
remove them to clean up the code a bit.
This allows smaller allocations to occur, closer to the actual
std::string's required size. This is particularly effective in
decreasing the allocation size upon initial construction (where
__recommend is called to determine the size).
Although the memory savings per-string are never more than 8 bytes per
string initially, this quickly adds up. And has lead to not insigficant
memory savings at Google.
Unfortunately, this change is ABI breaking because it changes the value
returned by max_size. So it has to be guarded.
To allow for a smoother transition, keep the safe mode working as is in
the LLVM 18 release (the first release that aims to make hardening
available), then deprecate it in LLVM 19.
This patch removes the non compliant constructor of std::future_error
and adds the standards compliant constructor in C++17 instead.
Note that we can't support the constructor as an extension in all
standard modes because it uses delegating constructors, which require
C++11. We could in theory support the constructor as an extension in
C++11 and C++14 only, however I believe it is acceptable not to do that
since I expect the breakage from this patch will be minimal.
If it turns out that more code than we expect is broken by this, we can
reconsider that decision.
This was found during D99515.
Differential Revision: https://reviews.llvm.org/D99567
Co-authored-by: Louis Dionne <ldionne.2@gmail.com>
This is useful when trying to run multiple tests with different
arguments to the executor script. This is needed in my case since I
do not know the correct ssh connection arguments when building libc++.
The testing script I have spawns multiple QEMU instances that listen on
a given port on localhost and runs lit with the --num-shards/--run-shard
argument. In order to connect each shard to the right QEMU instances I
need to customize the arguments passed to ssh.py (--extra-ssh-args and
--extra-scp-args) but can't do this at configure time since the target
port is only known when running the tests but not when calling CMake.
This change allows me to pass `executor=ssh.py <args>` to lit once I
know
the right hostname/port for running the tests.
This also deprecates the `LIB{CXX,CXXABI,UNWIND}_EXECUTOR` CMake
variable
as the same can be achieved by adding `executor=...` to the
`LIB{CXX,CXXABI,UNWIND}_TEST_PARAMS` variable.
Notice that because Holder<Incomplete> is _possible_ to complete, but
_unsafe_ to complete, that means that Holder<Incomplete>* is basically
not an iterator and it's not even safe to ask if
input_iterator<Holder<Incomplete>*> because that _will_ necessarily
complete the type. So it's totally expected that we still cannot safely
ask e.g.
static_assert(std::indirect_unary_predicate<bool(&)(Holder<Incomplete>&),
Holder<Incomplete>*>);
or even
static_assert(!std::indirect_unary_predicate<int, Holder<Incomplete>*>);
This was originally uploaded as https://reviews.llvm.org/D119029 and I
picked it up here as part of the Github PR transition.
Co-authored-by: Arthur O'Dwyer <arthur.j.odwyer@gmail.com>
This partially reverts commit e30a148b098, which removed the base
template for std::char_traits. That base template had been marked as
deprecated since LLVM 16 and we were planning to remove it in LLVM 18.
However, as explained in the post-commit comments in
https://reviews.llvm.org/D157058, the deprecation mechanism didn't work
as expected. Basically, the deprecation warnings were never shown to
users since libc++ headers are system headers and Clang doesn't show
warnings in system headers.
As a result, this removal came with basically no lead time as far as
users are concerned, which is a poor experience. For this reason, I am
re-introducing the deprecated char_traits specialization until we have a
proper way of phasing it out in a way that is not a surprise for users.
The safe mode is in-between the hardened and the debug modes, extending
the checks contained in the hardened mode with certain checks that are
relatively cheap and prevent common sources of errors but aren't
security-critical. Thus, the safe mode trades off some performance for
a wider set of checks, but unlike the debug mode, it can still be used
in production.
Differential Revision: https://reviews.llvm.org/D158823
This avoids having to add `_LIBCPP_ENUM_VIS`, since that is handled through `type_visibility` and GCC always makes the visibility of enums default. It also fixes and missing `_LIBCPP_EXPORTED_FROM_ABI` on classes when using Clang.
Reviewed By: ldionne, #libc
Spies: libcxx-commits
Differential Revision: https://reviews.llvm.org/D153658
In the event the internal function __init is called with an empty string the code will take unnecessary extra steps, in addition, the code generated might be overall greater because, to my understanding, when initializing a string with an empty `const char*` "" (like in this case), the compiler might be unable to deduce the string is indeed empty at compile time and more code is generated.
The goal of this patch is to make a new internal function that will accept just an error code skipping the empty string argument. It should skip the unnecessary steps and in the event `if (ec)` is `false`, it will return an empty string using the correct ctor, avoiding any extra code generation issues.
After the conversation about this patch matured in the libcxx channel on the LLVM Discord server, the patch was analyzed quickly with "Compiler Explorer" and other tools and it was discovered that it does indeed reduce the amount of code generated when using the latest stable clang version (16) which in turn produces faster code.
This patch targets LLVM 18 as it will break the ABI by addressing https://github.com/llvm/llvm-project/issues/63985
Benchmark tests run on other machines as well show in the best case, that the new version without the extra string as an argument performs 10 times faster.
On the buildkite CI run it shows the new code takes less CPU time as well.
In conclusion, the new code should also just appear cleaner because there are fewer checks to do when there is no message.
Reviewed By: #libc, philnik
Spies: emaste, nemanjai, philnik, libcxx-commits
Differential Revision: https://reviews.llvm.org/D155820
This has been deprecated and should be removed now.
Reviewed By: #libc, Mordante
Spies: Mordante, libcxx-commits
Differential Revision: https://reviews.llvm.org/D157058
This implements P0009 std::mdspan ((https://wg21.link/p0009)),
a multidimensional span with customization points for
layouts and data access.
Co-authored-by: Damien L-G <dalg24@gmail.com>
Differential Revision: https://reviews.llvm.org/154367
Existing notes were not fully correct and were missing a detail:
- `std::vector` was annotated long time ago,
- `std::deque` annotations are new,
- now container annotations were extended to all allocators (support in ASan API exists since LLVM16).
Reviewed By: philnik, #libc
Differential Revision: https://reviews.llvm.org/D156162
